The head of Moscow-controlled Crimea on Monday accused Ukraine of firing on oil drilling platforms off the coast of the peninsula that was annexed by Russia in 2014.

"This morning the enemy attacked the drilling platforms of Chernomorneftegaz," Sergey Aksyonov said on Telegram, referring to the Crimea-based oil and gas company.

"I am in contact with our colleagues from the defence ministry and the FSB (security agency), we are working on saving people," he added.

According to him, five people had been saved, three of them injured, while the search continued for others "with the involvement of patrol ships and aviation".

Aksyonov did not specify which platforms had been affected, but the Chernomorneftegaz operates several gas and oil fields in the Black Sea and in the Sea of Azov.

This is the first reported strike against offshore energy infrastructure in Crimea since Russia launched a military operation in Ukraine on February 24.