Russian forces have significantly increased the intensity of their combat activity in eastern Ukraine, Ukraine's top military commander Oleksandr Syrskyi said on Wednesday.

Russian President Vladimir Putin has declared a three-day ceasefire from May 8-10 to mark the 80th anniversary of the victory of the Soviet Union and its allies in World War Two. Ukrainian President Volodymyr Zelenskyy wants an immediate ceasefire lasting at least 30 days.

"Despite loud statements about readiness to cease fire for the May holidays, the occupiers (Russian forces) have significantly increased the intensity of combat actions, focusing their main efforts on the Pokrovsk direction," Syrskyi said on Telegram.

Reuters could not independently verify the battlefield situation, including the intensity of Russian combat actions.

Russian forces, which began their full-scale invasion of Ukraine in February 2022, have for months been trying to encircle the eastern town of Pokrovsk, a logistics hub, but Ukrainian resistance has slowed their advances in the area.

Moscow sees taking control of Pokrovsk as an important stepping stone to incorporating the whole of Ukraine's Donetsk region into Russia. Moscow de facto controls most of the region.

Kyiv and its allies reject Russia's territorial claims as illegal and accuse Moscow of prosecuting a war of colonial conquest.