Ukrainian troops remain in parts of the neighbouring Russian region of Kursk eight months after a cross-border incursion, though Russian forces have recaptured much lost territory.

In his nightly video address, Zelenskiy said Ukraine's top commander, Oleksandr Syrskyi, had presented a report "on the front line, our presence in the Kursk region and our presence in the Belgorod region."

"We continue active operations in the enemy's border areas and this is absolutely justified. The war must return to where it came from.

"Our main objective remains the same: to protect our land and our communities in the Sumy and Kharkiv regions from Russian occupiers."

He later referred to operations in the area by Ukraine's 225th Assault Regiment and congratulated the unit for its performance.

Zelenskiy repeated Kyiv's long-held contention that despite Russia's recapture of areas of Kursk in recent weeks, the operation was successful in that it drew Russian forces away from the war's main front line in Ukraine's Donetsk region.

"Due to the entire Kursk operation, we have managed to reduce pressure on other frontline sectors, particularly in Donetsk region," he said.

The president last month referred obliquely to "certain steps" undertaken by Ukraine's military in Russia "a little below the Kursk region", implicitly suggesting a presence in Belgorod region.

Russian military bloggers had reported battles in Belgorod region between Russian and Ukrainian troops.

On Sunday, Russia said its troops had seized the village of Basivka in Ukraine's northeastern Sumy region -- opposite Kursk -- and were battering Ukrainian forces in different settlements.

Russian President Vladimir Putin has repeatedly suggested that Russian forces carve out a buffer zone along the border.

A Ukrainian military spokesperson issued a new denial on Monday that Basivka was in Russian hands.