At least 15 people have died in overnight strikes across central and eastern Ukraine, in what Volodymyr Zelensky has described as one of Russia's "most vile" attacks.

Ukraine's president said a residential building in Pryluky in the Chernihiv region was destroyed as a "birthday 'gift' to Putin", who turns 74 on Wednesday. Strikes also hit Kyiv, Dnipro, Kremenchuk, Zaporizhzhia and Oleksandriya.

Zelensky said Ukraine had struck targets in attacks on Russia's Perm, Samara and Astrakhan regions in the past 24 hours, adding there was "also a response in the Black Sea", without providing further details.

Moscow is yet to comment on the latest strikes.

"The Russians wanted to strike painfully and demonstratively," Zelensky said, adding that 70 missiles were fired in total.

In the social media post on Wednesday morning, Zelensky said five people had been killed and 26, including five children, injured in a strike on a five-storey apartment building in Pryluky.

He added that people could still be trapped in the rubble.

Chernihiv Oblast police later reported that the death toll had risen to nine after the bodies of three children were recovered, with emergency workers continuing a search operation.

Two people were also killed and eight injured after Russian missile strikes damaged five apartment buildings in Dnipro and four high-rise buildings in Kremenchuk, said Zelensky.

Two people were also killed in the capital, Kyiv, and two others in Oleksandriya, he added.

Ukraine's national police posted pictures online showing what it says is an unexploded Russian Iskander missile in the middle of a Kyiv district. BBC Verify has confirmed the images are genuine and the apparent missile fragments came down in an area of open land surrounded by high-rise apartment buildings.

A video posted by the police shows people digging through collapsed remains of a residential building in Pryluky. Another verified video shows damage to cars and what appears to be rubble and a fallen tree in an area surrounded by apartment blocks in Kremenchuk.

Zelensky renewed a call for allies to provide air defence support packages to Ukraine, saying its military only managed to shoot down "some" of the missiles launched by Russia overnight.

According to Zelensky, one of the "key targets" of the attack was the country's energy infrastructure, which Moscow earlier said it would intensify strikes on following Ukraine's strikes on Moscow's energy facilities.

In a separate post on Wednesday, Zelensky said Ukraine had struck four targets in retaliatory attacks in the past 24 hours, including two oil facilities and a training ground in the Perm, Samara and Astrakhan regions.

"There is also a response in the Black Sea," the Ukrainian president wrote.

On Tuesday evening, footage emerged showing a huge plume of smoke engulfing an oil tanker off the coast of Sochi, along the Black Sea in southern Russia.

The Russian transport ministry later said unmanned boats had attacked the Liberian-flagged Aframax Rio oil tanker. Authorities claim the crew was rescued.

Separately, Bulgaria has halted a search for the missing crew of a ship that sank after being hit by a drone on Tuesday, Vice-Admiral Rumen Nikolov from the Maritime Administration Executive Agency said, as reported by Bulgarian television network Nora TV.

Tracking data shows the ship was anchored at the southern end of the Bosphorus strait until Monday when it entered the Black Sea heading north. Its last reported position on ship-tracking site MarineTraffic was at 23:43 GMT on Monday in what is known as the Bulgarian exclusive economic zone of the Black Sea.

Bulgarian specialist news outlet Maritime.bg reported the Alfa Watan was attacked by a drone and sank 70nm (130km) east of Byala.

As well as the civilian cargo ship, a second vessel - carrying grain - was also hit within Bulgaria's exclusive economic zone, its Prime Minister Rumen Radev said on Tuesday. The 18 crew members on the second vessel were rescued.

Bulgaria has not said who it believes was behind the attacks.

It comes as Russia intensifies strikes in the Black Sea, particularly the eastern side, as part of its war against Ukraine.

In an evening address on Tuesday, Zelensky claimed Russia was responsible for the attacks.

Moscow has not commented on the latest incident.