Russia claimed on Saturday that it foiled an attack on merchant ships in the southwestern Black Sea, blaming the strike on Ukraine.

The country’s Defence Ministry said the attack targeted “civilian transport ships” on Friday night with sea drones, or unmanned semi-submersible vehicles, according to maritime security firm Ambrey Analytics and a report by Reuters.

“The Russian Navy’s patrol ships and aircraft, which were on a mission in that area, were engaged to repel this attack,” the ministry said, according to Ambrey.