A fire erupted at a multistorey building in the Black Sea port city of Odesa late on Thursday following reports of drones the area, according to local authorities.
“A high-rise building in Odesa was damaged by a downed drone,” said Oleh Kiper, the regional governor, in a Telegram post.
Local Telegram channels shared images and videos of the fire, which appeared to affect the top two levels of the building.
Mr Kiper said that details on casualties were still being gathered and he advised residents to remain in shelters due to the ongoing drone attack.
Earlier on Thursday, a commercial vessel arriving to collect grain hit a Russian naval mine in the Black Sea, injuring two crew members, Ukrainian officials said.
The Panama-flagged ship was heading towards Ukraine's Danube port when it was damaged.
A captain and a sailor, an Egyptian citizen, were injured, with the latter taken to hospital in the city of Izmail, the head of the Odesa regional prosecutor's office said.
In the incident reported on Thursday the captain intentionally ran the ship aground to stop it sinking and Ukraine has sent out tugs that will tow it into port.
Moscow has increased attacks on Ukraine's port infrastructure since mid-July, when it quit a UN-brokered deal that allowed safe passage of Ukrainian grain shipments via the Black Sea.
Kyiv has since established an alternative route, which hugs the western shores of the Black Sea. It said Russian forces have been repeatedly dropping explosive devices in the vicinity.
Previously two civilian cargo ships were damaged by Russian mines, the Odesa Maritime Guard told AFP this month.
Ukraine has pushed back Russian warships in the western part of the Black Sea to allow some cargo ships in and out along a maritime corridor.
But the water is heavily mined, including by Russian planes, and is particularly dangerous in stormy weather.
The knock-on effects are potentially severe for buyers such as Lebanon, Sudan and Yemen, which rely on agricultural imports from Ukraine, one of the world’s most fertile countries.
