If confirmed, the cross-border foray would be among Ukraine's largest since Russia's full-scale invasion in February 2022, and unprecedented for its deployment of Ukrainian military units.
Putin is expected to meet North Korean leader Kim Jong Un for talks as they deepen their alignment in the face of separate, intensifying confrontations with Washington.
Such a deal appears a nonstarter for Kyiv, which wants to join the military alliance and has demanded that Russia withdraw its troops from all of its territory.
Ukrainian forces have secured "combat control" of areas where Russian troops entered the northeastern Kharkiv region earlier this month, President Volodymyr Zelenskyy said.
Chinese leader Xi Jinping and Russian President Vladimir Putin pledged to deepen their strategic partnership in Beijing on Thursday, in a stark show of their growing alignment as Moscow's troops advance in Ukraine.
US intelligence officials have determined Russian President Vladimir Putin likely didn't order the death of imprisoned opposition leader Alexei Navalny, an official says.
A draft peace agreement that Russia and Ukraine negotiated in the early days of the conflict could serve as a starting point for talks to end the fighting.
Ukrainian President said he'd listen to former US President's ideas to end the war in Ukraine with "pleasure" but trod carefully around the issue during an interview at the Delphi Economic Forum.
More than 400 people were detained in Russia while paying tribute to opposition leader Alexei Navalny, who died at a remote Arctic penal colony, a prominent rights group reported.