Five sailors have been rescued from a ship that sank 17 miles east of Krapets, the regional administration in Dobrich said. Another 11 crew members are missing. See our original report: Radev: new drone attacks in the Black Sea, one ship has sunk.

Earlier reports said one person had been rescued. One of the survivors was picked up by another ship in the area, and the other four are on a vessel. All will be taken to Varna. Dobrich regional governor Ruslan Tomov gave details of the rescue.

Drones also attacked another ship in the Black Sea, near Bulgarian territorial waters. The Chelsea 3 sent a distress signal at 1:30am, 18 miles east of Byala. A border police team rescued the whole crew and took them to the port of Varna. The maritime rescue centre in Varna responded as soon as the signal came in.

The crew numbers 15: seven Ukrainian citizens and eight from Azerbaijan. Five of them received medical help for minor injuries. The crew said three aerial drones hit the ship's deck and side.

The ship belongs to Ukraine and is registered in Odesa, but sails under the Maltese flag.

Prime minister Rumen Radev announced the attacks: one ship was hit and the other sank. He learned of the sunken ship at an emergency meeting of the Security Council at the Council of Ministers, footage of which is on his profile.

"Another attack on merchant ships very close to Bulgarian territorial waters is absolutely unacceptable," Radev said. He said there is no solid or clear evidence to blame any one side, but "the logic, as I have already said, points to the result being in favour of the Russian Federation".

Radev said Bulgaria wants support for an investigation into the strikes on the three ships, to establish exactly which country the drones came from. It also needs help to strengthen the monitoring of its air and sea space and its ability to respond.

The Russian ambassador, Mitrofanova, will be summoned for talks today. Bulgaria's permanent representatives to NATO and to the European Union have been informed. Radev is also due to speak with NATO secretary general Mark Rutte.