"On the front line, the Russian army is not observing the ceasefire and is not even trying to do so," he said in his Sunday evening speech.
Several people are reported killed or injured in Ukraine.
Among them, one person was killed and three were injured in Russian attacks on the Zaporizhia region, according to the region's governor.
In total, at least 16 more people have been injured in attacks around the country, according to Ukrainian authorities.
Russia's Defense Ministry, in turn, accuses Ukraine of thousands of ceasefire violations, including drone attacks.
President Donald Trump announced on Friday that Ukraine and Russia have agreed to a ceasefire between May 9 and 11.
