Ukrainian President Volodymyr Zelenskyy said on Saturday that Russian and North Korean forces suffered heavy losses in fighting in Russia's southern Kursk region.

Ukrainian and Western assessments say that some 11,000 North Korean troops are deployed in the Kursk region, where Ukrainian forces occupy swathes of territory after staging a mass cross-border incursion in August.

In his nightly video address, Zelenskyy quoted a report from top Ukrainian commander Oleksandr Syrskyi as saying that the battles had taken place near the village of Makhnovka, not far from the Ukrainian border.

"In battles yesterday and today near just one village, Makhnovka, in Kursk region, the Russian army lost up to a battalion of North Korean infantry soldiers and Russian paratroops," Zelenskyy said. "This is significant."

The president provided no specific details. A battalion can vary in size but is generally made up of several hundred troops.

Reuters could not independently verify the president's account.

Zelenskyy last week reported heavy North Korean losses in Kursk region, saying their forces were not being protected by the Russian forces they are fighting alongside.

He said North Koreans were taking extreme measures to avoid being taken prisoner and in some instances were being executed by their own forces.

In his latest remarks, Zelenskyy also said "fierce battles" had raged along the entire 620-mile front line, with the most difficult situation near the city of Pokrovsk.

Russian forces, he said, "continue to expend vast numbers of their own personnel in assaults."

A Ukrainian military spokesperson earlier said Pokrovsk remained the "hottest" front-line sector, with Russian troops launching fresh attacks near the town in an effort to bypass it from the south and cut off supply routes to Ukraine's troops.

The city, home to a mine that is the sole supplier of coking coal to Ukraine's once-giant steel industry, had a pre-war population of some 60,000 people. Ukraine estimates that around 11,000 of them remain in the city.