The Ukrainian Navy said on Saturday that reconnaissance had spotted a Russian unmanned vessel in an unspecified area of the Black Sea.
A Ukrainian naval drone was then deployed, manoeuvred close to the Russian vessel and opened fire with a heavy machine gun, sinking it, according to the Navy.
"This is the first naval battle in history between unmanned boats," the Ukrainian Navy said on X.
It also released a video showing gunfire and the destruction of a small vessel that could not be independently identified.
Both Ukraine and Russia have developed unmanned boats in recent months for a range of purposes.
These include explosive-laden vessels used to attack ships, as well as naval drones equipped with weapons such as machine guns or missiles.
Ukraine also says it operates vessels capable of carrying short-range drones close to the Russian coast.
Meanwhile, Russian air strikes in several Ukrainian regions have killed nine people, injured dozens and damaged residential buildings and infrastructure across the country.
The civilian death toll has risen sharply in Ukraine over the past two months as Russia steps up attacks on power plants and other infrastructure. Ukraine has hit energy facilities and warehouses in distant parts of Russia, and both sides have targeted each other's shipping.
Ukrainian President Volodymyr Zelenskiy said Russia had deployed nearly 500 drones against Ukrainian targets since early Saturday.
"Basically, the Russians have expanded the war away from the front, where they have no success, into the economy, and their tactics are as basic as it gets: destroying every site that could help people cope with the conditions of war," Zelenskiy wrote on X.
"Russia wants to kill the Ukrainian economy and break our resistance," Zelenskiy added.
The city council in Kramatorsk, one of Ukraine's frontline "fortress cities" that Russia wants to capture, said Russian forces attacked private cars, killing three people in three incidents over a 90-minute period. Four people were injured.
"These are not military targets," the council said.
"They are ordinary civilian cars. People were going about their business."
The governor of Ukraine's Zhytomyr Region, west of Kyiv, Vitaliy Bunechko, said a Russian strike on a grocery store killed two people in the town of Zvyahel. Bunechko said two petrol stations also came under attack as well as an unidentified "enterprise with foreign investment".
Earlier, Zelenskiy reported attacks on the southeastern city of Zaporizhzhia and Kryvyi Rih, his hometown.
The governor of Zaporizhzhia Region, Ivan Fedorov, said two people were killed and 11 injured in assaults on Zaporizhzhia and other localities.
Oleksandr Vilkul, head of Kryvyi Rih's military administration, said two people were killed in overnight attacks on the city by drones and missiles.
The Russian military said its forces hit Ukrainian steel maker Zaporizhstal in the city of Zaporizhzhia, an Interpipe Steel complex in Dnipro and several plants in Kryvyi Rih, including the Northern Iron Ore Beneficiation Works complex.
In Odesa Region, Governor Oleh Kiper said 37 people, including a baby, were injured in a series of overnight attacks. Two people were missing.
In Moldova, on Ukraine's western border, authorities closed national airspace for nearly an hour after a drone was detected near the border. Seven border crossings were temporarily closed.
Russian drones have regularly entered Moldovan airspace despite official protests. During one instance this week, the departure of Zelenskiy's aircraft to Norway was delayed.
with dpa
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