A US Navy P-8 Poseidon plane is patrolling over the Black Sea after a rise in drone attacks on merchant ships off the Bulgarian and Romanian coasts.

Bulgaria's defence ministry has announced extra security measures along the Black Sea coast. It said yesterday that the Bulgarian army is using drones to watch the coast and the air and sea space in front of it, and warned residents that drones over the coast may be part of this monitoring. The ministry says the flights are a precaution and should give early information on the situation.

How it all started: Army uses drones to watch Bulgaria's Black Sea coast

Aleksandar Trapchev, head of a fishing association, told BNT that ships no longer go out to sea at night because crews fear debris from the fighting.

Trapchev said wreckage from drones often floats in the sea, and that shots were fired a few days ago. "This is unacceptable, people are working in fear," he said.

He also warned about an abandoned ship between Bulgaria and Romania, near the Romanian border. It has no lights and is a danger to shipping. A small fishing boat ran into it a few days ago.