According to local media reports, Ukrainian forces had fired at North Korean soldiers in combat for the first time since their deployment by Russia to its western Kursk region.
About 11,000 North Korean troops have now reached the Kursk border region in Russia, Ukrainian President Volodymyr Zelenskyy has said.
In his nightly address on Monday, the Ukrainian leader criticised the West for its muted response, saying, ''we see an increase in North Koreans, but we do not see an increase in the reaction of our partners."
He said more counter-efforts are needed to stop Pyongyang from deploying its soldiers into the fray.
"In particular, the issue of air defence is important. Everyone can see how much more Russians are using shaheds and air bombs. This terror is growing every month. More countermeasures are needed," Zelenskyy added.
According to local media reports, Ukrainian forces fired at North Korean soldiers in combat for the first time since their deployment to fight alongside Russian forces in Kursk.
If confirmed, this would mark the first direct intervention by a third army since Russia began its full-scale invasion of Ukraine nearly three years ago.
Since August, Ukrainian troops have held large swaths of Kursk after Kyiv launched a surprise cross-border incursion into the Russian region.
In September, Moscow's forces ramped up fighting in the region to reclaim lost territory, according to the Kremlin.