Russia on Friday returned to Ukraine the bodies of 501 soldiers, Ukrainian authorities said, in what appeared to be the biggest repatriation of war dead since Russia’s full-scale invasion in February 2022.

Most of the soldiers were killed in action in the eastern Donetsk region of Ukraine, mostly around the city of Avdiivka that Russian forces captured in February after a long and grueling battle, Ukraine’s Coordination Headquarters for the Treatment of Prisoners of War said in a statement.

Law enforcement agencies and forensic experts will identify the victims, who will then be handed over to family members for burial, it said.

The war is believed to have killed tens of thousands of soldiers on each side, though there are no official or independently collated figures.

Ukrainian President Volodymyr Zelenskyy this week disclosed parts of his so-called ‘victory plan’ aimed at compelling Russia to end the war through negotiations.

That proposal is being considered by Ukraine’s Western partners, whose help is vital for Kyiv to resist its bigger neighbor. A key element would be a formal invitation into NATO, which Western backers have been reluctant to consider until after the war ends.

Russian President Vladimir Putin said Friday that Moscow is prepared to enter talks. He welcomed peace proposals previously tabled by China and Brazil, saying they could “serve as a good basis for a search for peace.” Those proposals have failed to convince Kyiv.

Speaking during a meeting with media leaders from the BRICS bloc of developing economies, Putin ruled out any concessions regarding the status of the four Ukrainian regions that Moscow illegally annexed in September 2022, saying that “those are our territories.” That would be unacceptable for Ukraine.

U.S. President Joe Biden met Friday in Berlin with some European leaders and said that Ukraine’s Western allies must keep up their support for Kyiv.

Zelenskyy says Russia is getting help from China, Iran and North Korea.

South Korea’s spy agency said Friday that North Korea has dispatched troops to support Russia against Ukraine.

The head of Ukrainian Military Intelligence, Kyrylo Budanov, was quoted as saying 11,000 North Korean troops are currently training in Russia to join the fight against Ukraine.

Budanov told defense news website The War Zone on Thursday that the first 2,600 North Korean soldiers are preparing to reinforce the Russian army in Kursk, the Russian border region where a Ukrainian incursion has held land since early August.

The fighting has continued unabated while world leaders debate their next steps.

Russia launched 135 Shahed drones, as well as some other unidentified drones, at various parts of Ukraine on Thursday night, the Ukrainian air force said, in what was one of the biggest single drone barrages of the war.

Most of the drones were intercepted, the air force said. There was no official word on casualties or damage.