Two merchant ships were hit by drones in the Black Sea near Bulgarian territorial waters, and one of them sank, Prime Minister Rumen Radev said. The crew of the first ship, hit 18 miles east of Byala, was rescued. The second sank 17 miles east of Krapets, and one crew member was rescued there.

Earlier we reported that the prime minister will summon Russian ambassador Eleonora Mitrofanova over the new attack. Below are the details of the strikes themselves.

Footage of the emergency meeting of the Security Council at the Council of Ministers, which Radev called, was posted on his Facebook page. "Yet another attack on merchant ships right next to Bulgarian territorial waters is absolutely unacceptable," the prime minister said. He will summon Russian ambassador Mitrofanova for talks today.

The first ship is the Chelsea 3. It flies the Maltese flag, is registered in Odesa and is owned by Ukraine. The crew say three aerial drones hit it, on the deck and on the side of the hull.

The distress call from a ship off Byala came in at 1:30am. The Maritime Rescue Coordination Centre in Varna responded at once, and Bulgaria's emergency and rescue teams were sent out. A Border Police crew rescued everyone on board, seven Ukrainian citizens and eight citizens of Azerbaijan, during the night.

The sailors were taken to the port of Varna. Five of them are receiving medical care, and the authorities say their injuries are minor.

News of the second ship came in during the meeting. Bulgaria is also running a search and rescue operation in the Black Sea tonight, Radev said.

Bulgaria's permanent representatives to NATO and the EU have been informed. The prime minister is also due to speak to NATO Secretary General Mark Rutte.

Radev said Bulgaria will keep pressing for help to watch its airspace and waters more closely and to strengthen its ability to respond.

Bulgaria continues to ask for support for the investigation into the attacks on three ships, to establish which country the drones came from. Radev admitted there is no solid, clear evidence to blame any of the parties. "As I have already said, logic points to the result being in favour of the Russian Federation," he added.