Bulgarian PM summons Russian ambassador after ship sinks in Black Sea drone attack

Five crew members on the Ukrainian-registered merchant ship suffered minor injuries in Tuesday's attacks

Bulgarian Prime Minister Rumen Radev has summoned the Russian ambassador after two merchant ships were struck by drones off Bulgaria's Black Sea coast.

The other vessel, Ukrainian owned, was hit by drones 18 nautical miles from the town of Byala and all 15 crew were rescued.

Radev convened an emergency meeting on Tuesday and said he had summoned Russian envoy Eleonora Mitrofanova. Although there was no conclusive evidence of blame on "either side... the logic suggests that the outcome benefits the Russian Federation", he said.

Bulgaria is a Nato member, and Radev also spoke to secretary general Mark Rutte about the latest attacks.

"We have already strengthened our posture along the eastern flank and will continue to monitor the security environment, adjusting our deterrence and defence posture as needed," he added.

If this had happened just a few nautical miles to the west, Article 5 of the Nato treaty could have been triggered. The article defines an armed attack on one member of the military alliance as an attack on all.

Radev came to office during the summer and has since rejected suggestions that he is "pro-Russian".

Russia's military has not publicly commented on the issue. It has recently intensified its strikes on vessels in the Black Sea, particularly the western side, as part of its war against Ukraine.

Moscow says it is targeting ships delivering weapons and dual-use cargo to Ukrainian ports - and cited attacks in the ports of Mykolaiv and Chornomorsk last week, along with one in the Black Sea.

Rumen Radev (middle right) said the attack was "absolutely unacceptable" before meeting Russia's ambassador Eleonora Mitrofanova (middle left)

Meeting with his security chiefs on Tuesday, Bulgaria's prime minister said: "Another attack on merchant ships in the immediate vicinity of Bulgarian territorial waters is absolutely unacceptable".