Both the Kremlin and Pyongyang deny that they have engaged in military transfers. And NATO Secretary General Mark Rutte said Friday that he “could not confirm reports that North Koreans are now active as soldiers involved in the war effort.”

But Putin and North Korean leader Kim Jong Un signed a comprehensive strategic partnership treaty last summer that obliges both countries to provide each other with military assistance if either is attacked. South Korean President Yoon Suk Yeol warned on Friday that Pyongyang’s involvement in the conflict in Ukraine would pose a “serious security threat” to the world.

“This is a huge threat of further escalation of Russian aggression against Ukraine,” Ukraine’s Sybiha said on Saturday, Reuters reported. “There is a high risk that the country will grow beyond its current size and borders,” he said.

France’s Barrot said such a move would send a signal that Moscow was struggling in the war. But “it would be serious and push the conflict into a new phase, an additional escalating phase,” Barrot said.

Meanwhile, Russia and Ukraine carried out a new prisoner of war exchange on Friday, with the countries repatriating 95 prisoners each. The United Arab Emirates facilitated the agreement and acted as a mediator.

“Every time Ukraine rescues its people from Russian captivity, we bring closer the day when freedom will be returned to all those still held in Russian captivity,” Zelenskyy said in a post on X.