This was CNBC's live blog tracking developments on the war in Ukraine.

Russian President Vladimir Putin on Friday was quoted as saying that capturing Ukraine's second-largest city of Kharkiv is not part of Moscow's current plan.

Speaking at a news conference in China, Putin said that Russian forces operating in the area may be forced to create a "sanitary zone" to shore up Russia's own security, according to Russian state news agency Ria Novosti.

His comments come as Ukrainian forces scramble to hold off Russia's latest push to make further gains in Ukraine's northeastern region.

Ukrainian President Volodymyr Zelenskyy told reporters that the country's defense forces had "stabilized" the situation around Kharkiv after Russian forces advanced 10 kilometers (6.2 miles) into the northeastern region.

An air raid alert in Kharkiv lasted more than 16-and-a-half hours, Reuters reported, citing Ukraine's public broadcaster Suspilne. It marked the longest recorded air alert since Russia launched its full-scale invasion of Ukraine in February 2022.

Russian authorities on Friday said that a massive Ukrainian drone attack set a major Russian oil refinery ablaze and caused power outages in Crimea's largest city of Sevastopol.

Russia says it has captured 12 settlements in Ukraine's Kharkiv region over the past week

Russia's Defense Ministry on Friday said it had captured 12 settlements in Ukraine's northeastern Kharkiv region in the last week, before adding that it "continues to advance into the depths" of the country.

CNBC could not independently verify developments on the ground.

Russian President Vladimir Putin said earlier in the day that Russian forces operating near Ukraine's second-largest city could be forced to create a buffer zone to shore up security.

Putin added that the Kremlin's current plan was not to capture the city of Kharkiv.

— Sam Meredith

Airport in Russia's Mineralnye Vody catches fire - RIA

An airport in the city of Mineralnye Vody in southern Russia caught fire on Friday during construction work, state-run RIA news agency reported citing emergency services.

SHOT media outlet reported the arrivals terminal was ablaze and TASS news agency said that fire brigades were on their way to the scene.

Pictures shared in Russian Telegram channels showed thick smoke billowing from the building.

— Reuters

Britain says it is targeting Russia and North Korea 'arms-for-oil' trade partnership with new sanctions

Britain said on Friday it was targeting Russia and North Korea's "arms-for-oil" trade partnership as it announced a package of new sanctions against three companies and one individual.

The U.K. said the measures, which were issued alongside its international partners, highlight what it described as the "joint malign efforts" of Russia and North Korea to contravene or circumvent United Nations sanctions.

"[Russian President Vladimir] Putin is straining every sinew to sustain his illegal war in Ukraine, even resorting to illicit 'arms-for-oil' trade deals with the DPRK, blatantly violating UN sanctions that Russia itself voted for, and vetoing UN Monitoring panels that report on their activity," U.K. Foreign Secretary David Cameron said in a statement.

Earlier on Friday, the North Korea's leader's sister denied supplying weapons to Russia. Moscow has previously rejected allegations that North Korea is supplying arms to the country.

— Sam Meredith

Putin says capturing Kharkiv is not part of Russia’s current plan

Russian President Vladimir Putin on Friday said that capturing Ukraine's second-largest city of Kharkiv is not part of Moscow's current plan, according to Russian news agency Ria Novosti.

Speaking at a news conference in China, Putin said that Russian forces operating in the area may be forced to create a "sanitary zone" to shore up Russia's own security. His comments come as Ukrainian forces scramble to hold off Russia's latest push to make further gains in Ukraine's northeastern region.

Putin was quoted as saying that Russian forces in the Kharkiv region were moving strictly according to the Kremlin's plan, without providing any further details.

Ukrainian President Volodymyr Zelenskyy said earlier on Friday that Kyiv's forces had "stabilized" the situation in Kharkiv after Russian troops advanced 10 kilometers (6.2 miles) into the territory.

— Sam Meredith

Russia and China to sign Power of Siberia-2 gas pipeline contract 'in near future', says Novak

Russia and China expect to a sign a contract "in the near future" on the Power of Siberia-2 gas pipeline, which will carry Russian gas to China, Russian Deputy Prime Minister Alexander Novak was cited as saying by Interfax late on Thursday.

Russia has been in talks for years about building the Power of Siberia-2 pipeline to carry 50 billion cubic metres of natural gas a year from the Yamal region in northern Russia to China via Mongolia.

Novak, President Vladimir Putin's top oil and gas point man, is part of the official Russian delegation currently on a visit to China, though Gazprom CEO Alexei Miller is not.

Putin and China's Xi Jinping have pledged a "new era" of strategic partnership on the trip as the Russian leader increasingly turns to China to support his wartime economy.

— Reuters

Russian forces expanded area of active combat by nearly 70 kilometers, Ukraine army chief says

Russian forces have expanded the area of active combat by nearly 70 kilometers (43.5 miles) by launching their latest offensive in the northeastern Kharkiv region, Ukraine's Commander-in-chief Oleksandr Syrskyi said on Friday.

In a Google-translated post on Telegram, Syrskyi said Russian forces had sought to force Ukraine to deploy additional reserve brigades into the fighting.

"The enemy launched an offensive well ahead of schedule when he noticed the overturning of our troops, however, he failed to break through our defenses," Syrskyi said. "However, we understand that there will be tough battles ahead and the enemy is preparing for it."

Syrskyi said Ukrainian forces were preparing to defend the northern Sumy region.

— Sam Meredith

Ukrainian drone attack sets major Russian oil refinery ablaze, causes power outages in Crimea

A massive Ukrainian drone attack set a major Russian oil refinery ablaze and caused power outages in Crimea's largest city, according to Russian authorities.

The operational headquarters for the Krasnodar region in southern Russia said on Friday that debris from intercepted Ukrainian drones had caused a fire at an oil refinery in Tuapse. The fire has since been extinguished and no casualties were reported.

CNBC could not independently verify developments on the ground.

Separately, power supplies were cut off in parts of Sevastopol as debris from a Ukrainian drone fell onto a power station, according to Mikhail Razvozhayev, the Crimean city's Russia-installed governor.

Restoring the power supplies could take up to 24 hours, Razvozhayev said via Telegram, while school and kindergartens have been suspended. No casualties were reported.

— Sam Meredith

Zelenskyy says situation in Kharkiv region 'stabilized' after Russian forces make significant gains

Ukrainian President Volodymyr Zelenskyy said on Friday that Russian forces had advanced 10 kilometers (6.2 miles) into Ukraine's northeastern Kharkiv region, Reuters reported, citing the media outlet RBC-Ukraine.

Zelenskyy told reporters that Ukrainian forces had now "stabilized" the situation, however. His comments come as Russian forces seek to build on recent gains in Ukraine's second-largest city.

"Today, our defence forces have stabilised the Russians where they are now. The deepest point of their advance is 10 km," Zelenskyy said.

— Sam Meredith

Russia urges U.S. to respond to its prisoner swap proposals

Russian Deputy Foreign Minister Sergei Ryabkov on Friday urged the U.S. to respond to its prisoner swap proposals, state news agency TASS reported, blaming Washington for slow progress and calling for "a realistic search for solutions."

"Who may be exchanged and under what scheme is a separate issue. The Foreign Ministry is not a direct participant in these exchanges, and the talks are held via a dedicated channel of communication, but, generally speaking, I can say that the US has not perceived our proposals until now," Ryabkov told TASS in an interview.

"Nevertheless, we call upon them to focus on a realistic search for solutions on the basis of Moscow's proposals, which they are well aware of," he added.

A spokesperson for the U.S. State Department was not immediately available to comment when contacted by CNBC.

— Sam Meredith

Japan says use of frozen Russian assets for Ukraine must align with law

Japanese Finance Minister Shunichi Suzuki said on Friday proposals to use frozen Russian financial assets to aid Ukraine needed to comply with international law.

Finance ministers from the Group of Seven major democracies will meet in Italy next week and will discuss the question of how revenues from the frozen Russian assets should be used.

"Japan will join the discussions at the upcoming meeting from this basic standpoint," Suzuki said during a regular post-cabinet meeting press conference.

The G7 froze around $300 billion worth of financial assets soon after Russia's attack on Ukraine in February 2022.

Since then, G7 countries and the European Union have debated whether and how to use the funds to help Ukraine.

— Reuters

Kharkiv hit by several drone strikes during Ukraine's longest air raid alert of the war

Ukraine's second-largest city of Kharkiv was hit by several drone strikes overnight, according to its regional governor, during the country's longest air raid alert since Russia launched its full-scale invasion.

Kharkiv Governor Oleh Syniehubov said late Thursday in a Google-translated post via Telegram that Russian forces attacked the country's northeastern city with at least five drone strikes. It wasn't clear whether there had been any casualties.

CNBC could not independently verify developments on the ground.

An air raid alert in the city lasted more than 16-and-a-half hours, Reuters reported, citing Ukraine's public broadcaster Suspilne. It marked the country's longest recorded air alert since Russia launched its war with Ukraine in February 2022.

Syniehubov said on Friday that Ukrainian forces repelled eight attacks from Russian forces in the Liptsy, Staritsa and Vovchansk areas of the Kharkiv region.

— Sam Meredith

Putin says Russia and China can be proud of economic cooperation

Russia and China can be proud of their economic cooperation, Russian President Vladimir Putin said on Friday, adding that Moscow stood ready to supply Beijing with clean energy.

Speaking at a Russia-China Expo in the Chinese city of Harbin during a state visit, Putin said Russia was building a tight strategic cooperation with China.

He added that Russia was in the process of diversifying its supplies to China, including through agriculture exports such as fish, crops and pork.

Putin on Thursday heaped praise on Chinese President Xi Jinping at the start of his two-day state visit and thanked Beijing for its efforts in trying to solve what he described as the Ukraine "crisis."

Russia's full-scale invasion of Ukraine entered its third year in late February.

— Sam Meredith

'Brothers forever': Putin says Russia-China relations are at highest level in history

Russian President Vladimir Putin on Thursday described Russian and Chinese people as "brothers forever," in a speech before a concert in Beijing marking 75 years of diplomatic relations between the countries.

Putin said Russia-China relations were at their "highest level in history" with the "character of genuine comprehensive partnership and strategic interaction," according to an English transcript published by the Russian presidential office.

"A well-known song of that time, 75 years ago, is often performed today. It has a sentence that has become a catch phrase – "Russian and Chinese are brothers forever." I am confident that we will continue strengthening harmonious Russia-China partnership in this fraternal spirit," Putin said.

The countries have repeatedly emphasized their friendly relations and so-called "no limits partnership," with Beijing embroiled in trade disputes and Moscow largely alienated by the west.

— Jenni Reid

Zelenskyy meets military leaders in Kharkiv as Russian offensive advances

Ukrainian President Volodymyr Zelenskyy has travelled to Kharkiv in northeast Ukraine, where he was briefed on the battlefield situation as Russia's new offensive makes progress.

Zelenskyy said on Telegram that he had met with Ukraine's army chief Oleksandr Syrskyi and with other military officials to discuss the "operational situation, tasks and needs of each involved brigade, each unit, in particular in the Kharkiv Region, in the Vovchansk and Lyptsi districts," according to a NBC News translation.

Both areas are seen as hotspots in the war, with Russian forces occupying parts of Vovchansk and on the brink of seizing Lyptsi, according to Russian officials.

Ukraine's military said earlier on Thursday that it was slowing Russia's advance and that its units "continue to carry out combat missions within the Vovchansk urban development in the northern part of the city, keeping the enemy under fire control."

CNBC was unable to verify the battlefield assessments.

In his latest update, Zelenskyy conceded that the situation in the Kharkiv region "remains extremely difficult," but that it was "generally under control." He added that Ukraine was "strengthening our units."

Ukraine's current combat situation, forthcoming threats and "Ukrainian opportunities to counter Russian offensive plans" were also discussed, Zelenskyy said.

In a subsequent post, the Ukrainian leader said he had also visited soldiers who were wounded fighting in Kharkiv.

— Holly Ellyatt

Read CNBC's previous live coverage here:

Putin heaps praise on Xi while in China; Russia says forces advancing 'in all directions' in Ukraine