"In the past 24 hours, Ukrainian armed forces drove the enemy away from more than 20 settlements" and are regaining "full control over them", the Ukrainian army said in its daily briefing.

"In their retreat, Russian troops are hastily abandoning their positions and fleeing," the army statement added.

Throughout the weekend, Ukraine claimed sweeping successes against Russia in the south and the east, including the cities of Izyum, Kupiansk and Balakliya.

On Sunday night, regions in eastern Ukraine saw widespread electricity blackouts after strikes described by foreign ministry spokesman Oleg Nikolenko as an "act of desperation following Russia's immense losses and retreat in eastern Ukraine".

There was "a total blackout in the Kharkiv and Donetsk regions, a partial one in the Zaporizhzhia, Dnipropetrovsk and Sumy regions", Ukrainian President Volodymyr Zelensky said in his daily address on Sunday.

Power was quickly restored in most places.

In the Kharkiv region 80 percent of the water and electricity supply had been restored on Monday morning, according to the deputy head of the president's office, Kyrylo Tymoshenko.