A Russian "guided bomb" has hit a blood transfusion centre in north-eastern Ukraine, killing and injuring people, Ukraine's president has said.

Volodymyr Zelensky did not give details on how many people had been killed or injured in Saturday's attack in Kupiansk in the Kharkiv region.

"This war crime alone says everything about Russian aggression," he said.

Russia has not commented. It has previously denied all allegations of targeting civilians - or war crimes.

The BBC has not been able to verify the report.

The city of Kupiansk and nearby settlements were seized by Russian troops in the first few days of Moscow's full-scale invasion of Ukraine, launched in February 2022.

The area was liberated during a Ukrainian counter-offensive last September.

In a post on social media, Mr Zelensky described the perpetrators as "beasts".

"Defeating terrorists is a matter of honour for everyone who values life," he added.

President Zelensky also said that on Saturday Russia separately carried out a missile attack, targeting an aeronautical company run by group Motor Sich in the western Khmelnytskyi region.

The Russian strikes come after Moscow accused Ukraine of hitting a Russian tanker with 11 crew members in the Black Sea - the second such sea drone attack in as many days.

Russian maritime officials said the engine room of the Sig tanker was damaged in the attack in the Kerch Strait. No-one was injured.

The Kerch Strait connects the Black Sea and the Sea of Azov, separating Crimea - Ukraine's peninsula annexed by Moscow in 2014 - and Russia's Taman peninsula.

Ukraine has not publicly commented. But a Ukrainian security service source told the BBC a sea drone had been used.