An oil tanker off Russia’s Black Sea coast was struck by a naval drone, triggering a huge fire and black smoke cloud that blanketed parts of the resort city of Sochi, Russia’s transport ministry has said.

The transport ministry said a Liberian-flagged tanker had been attacked and that “crude oil is burning openly in the waters of the Black Sea”.

“Firefighting efforts will begin once the fire’s intensity has subsided and rescue vessels can safely approach the tanker,” the ministry said.

A crew of 23 – all Indian citizens – had been rescued, it added.

Russia and Ukraine have targeted commercial shipping around the Black Sea since the conflict began, and Russia has recently attacked grain vessels carrying Ukrainian goods near the coast of Romania.

There was no comment from Kyiv on the attack.

Videos and photos circulated on social media from Sochi – a popular Black Sea resort city of almost 500,000 people – showed bright orange flames out at sea and a thick column of black smoke billowing into the sky.

Local officials restricted access to the coast and beaches.

Elsewhere on Tuesday, Bulgaria’s prime minister said that two commercial vessels were had been struck by drones in the first attack on shipping in the Nato member’s exclusive economic zone in the Black Sea.

Bulgarian authorities said that the origin of the drones was under investigation, but Ukrainian President Volodymyr Zelenskyy blamed Russia for the drone strikes. Bulgarian prime minister Rumen Radev condemned the attack.

After an emergency government meeting, Radev said: “This is an unacceptable attack in Bulgaria’s exclusive economic zone. It is a blatant violation of international law and maritime law.” Radev said after an emergency government meeting.

Sea and aerial drones attacked the ships about 80 miles (128km kilometers) off Bulgaria ’s coast, he said.

Zelenskyy warned in his nightly address on Tuesday that a “massive strike” from Russia was likely to come, and in the early hours of Wednesday Kyiv was attacked.

Russian strikes damaged buildings and warehouses across the Ukrainian capital, Kyiv’s mayor ​Vitali ‌Klitschko said ‌on Telegram.

Agence France-Presse reported multiple explosions in Kyiv, and Reuters reported two people were killed by Russian strikes.

A separate Russian strike on Ukraine’s south-eastern city of Dnipro damaged ⁠an industrial facility, ​officials said, without giving details.

Kyiv has been under increased attack as winter approaches, with Russian airstrikes targeting energy infrastructure, rail and road transport, including bridges that connect the city over the Dnipro river. Air raid sirens have sounded almost constantly day and night, urging residents to take cover in basements, shelters and subway stations.

With Reuters and Agence France-Presse