The Defence Ministry said the attacks occurred on Friday during a three-day ceasefire running from Thursday to Saturday that Russia has unilaterally declared to mark the 80th anniversary of victory over Nazi Germany in World War II.
Ukraine has called the ceasefire a "farce" and on Friday documented scores of armed clashes.
It noted in particular, northeastern Sumy region, site of some of the heaviest Russian assaults in recent weeks, saying there had been no letup during the Kremlin-inspired ceasefire.
"There has been no 'ceasefire' in Sumy region on the 8th or 9th of May. Over the two days Russia has killed three civilians, the region's military administration said on Telegram.
Ukraine's military, in its account late on Friday of battlefield operations, said 162 armed clashes had been recorded over the past 24 hours, with the Kremlin ceasefire in effect, along with 22 air strikes and 956 drone attacks.
It noted heavy fighting near Pokrovsk, a logistics hub in eastern Ukraine targeted by Moscow's troops for months. Russian forces had attempted to break through Ukrainian lines 51 times.
The Russian Defence Ministry account said it had registered four attempts by Ukrainian forces to smash through the border into the Kursk and Belgorod regions in the past week.
In eastern Ukraine, Kyiv's troops had attacked Russian forces 15 times during the ceasefire, the ministry said.
Ukraine has said Russia had repeatedly breached its own truce this week. The governor of the southeastern Zaporizhzhia region said on Friday that Russia hit eight Ukrainian frontline villages 220 times since the ceasefire went into effect.
In Russia's Belgorod border region, the local governor said a Ukrainian drone had attacked a government building on Friday.
In Kursk, Ukrainian troops launched a major incursion in August and held onto a chunk of Russian territory for many months as Moscow's forces battled to eject them with help from North Korean soldiers. Some fighting has continued, even after Putin in April declared "victory" in Kursk.
Ukraine said its troops had repelled 19 attacks in the region.
Rybar, a pro-Russian war blogger, said there was "high-intensity fighting" between Russian and Ukrainian troops near Tetkino, a village in the region. Rybar and other bloggers said Ukrainian attacks on multiple villages in the neighbouring Belgorod region were continuing on Friday.
Reuters could not independently verify statements by war bloggers or battlefield reports from either side.
Ukraine and Russia both accused the other of repeatedly violating a previous 30-hour Easter ceasefire declared by Putin.
