Two ships have been hit in a drone attack in the Black Sea off the coast of Bulgaria, a week after a similar incident.
The Prime Minister of Bulgaria Rumen Radev wrote on social media that a Ukraine-owned ship was 'hit by three aerial drones', and shortly after another ship was hit and sank.
He said he intended to summon the Russian ambassador over the 'absolutely unacceptable' attacks.
One crew member from the sunken vessel was rescued, he said, without providing details on the others aboard. He said it was struck 17 nautical miles east of Krapets.
The Ukrainian-owned 'Chelsea 3', sailing under Maltese flag, was damaged some 18 nautical miles east of Byala around 1.30am (2230 GMT).
Its crew - seven Ukrainians and eight Azerbaijanis - had been rescued and safely transported to the port of Varna. Five crew members received medical assistance, but no one was seriously injured.
He called on NATO and the European Union for assistance, saying Bulgaria lacked clear evidence to identify who was responsible.
'Bulgaria continues to seek support for an investigation into the attacks to determine the country of origin of the drones,' he said.
Crew members from a ship damaged in a drone attack on October 6 disembark from a Bulgarian border police vessel in Varna, Bulgaria
Bulgarian authorities take an injured crew member to a hospital after two commercial vessels were attacked in the NATO member's Black Sea economic zone on October 6
'We are also seeking assistance to strengthen surveillance of the air and maritime domains and enhance our response capabilities.
'We do not have clear and conclusive evidence to attribute responsibility to either side.
'However, as I have already stated, the logic suggests that the outcome benefits the Russian Federation.'
European Commission President Ursula von der Leyen said those responsible for the drone attacks must be held accountable.
She said the Black Sea had become another front of escalation in the Russian war against Ukraine, calling such attacks 'unacceptable'.
Ukraine's Foreign Minister Andriy Sybiga directly blamed Russia for the attacks, denouncing what he called Moscow's 'deliberate disregard for civilian lives and maritime security in the Black Sea'.
'The Black Sea is a lifeline for global food security. Russia is attacking it to weaponise hunger and hold the world hostage,' he posted on X.
Last Tuesday, a merchant ship was sunk off the coast of Bulgaria while another was rescued after they were struck by drones.
It is not clear who carried out the attacks but Radev described it as a gross violation of international law.
The ship, named Alfa Watan, sank around 70 miles off the coastal town of Byala and a rescue party was launched but the crew on board are still missing.
A Bulgarian ferry that witnessed the explosion rushed to the scene and discovered overturned life rafts and jackets near the ship that sank, but no crew were found.
Shipping sources said they appeared to be the first such attacks in Bulgarian waters.
It comes amid growing concerns about hybrid attacks by Russia as it wages war in Ukraine.
While the search for the Alfa Watan crew was called off, survivors on the vessel Able, which was carrying grain, were rescued.
All 18 crew members – 11 Turkish and seven Indian – were saved but two were injured and flown to a hospital in the port city of Varna.
The other, which sank, was a Togo-flagged ship whose cargo was not disclosed and it is unclear how many people were on board.
Radev said it was unclear where the drones came from but Russia is suspected to be behind the incident.
The cargo ship Alfa Watan is pictured in Turkey just one day before it was struck by a drone
The cargo vessel Able is pictured off the Turkish coast
Bulgaria, a Nato member, does not border either Russia or Ukraine but it holds a strategic position in the Black Sea, where the warring nations have major ports.
The incident occurred some 140 nautical miles away from the Ukrainian coast.
A maritime security source said initial assessments of the strike suggested it had probably been a Russian attack.
Radev did not say who was behind the incident but made a reference to Russia's war in Ukraine.
He said: 'If this war is not brought to an end in time, it will continue to expand its geographical scope and increase the risk of even a global conflict.
'We are seeing the war intensify, with all the rules of international law now being violated, and civilian vessels being attacked at sea. This is absolutely unacceptable.'
The Bulgarian leader added: 'As a state responsible within our exclusive economic zone for the health and lives of anyone navigating in this area, regardless of who is responsible, we are obliged to conduct emergency search and rescue operations.
'What is happening is seriously disrupting shipping in the Black Sea, driving up insurance costs even further and making shipping extremely difficult.'
Russia did not immediately comment on the incident.
Von der Leyen said that attacks on civilian shipping are unacceptable.
She said: 'Commercial ships – and innocent crews – are being targeted, with lives already lost at sea.'
Hungarian prime minister Peter Magyar meanwhile said: 'Hungary stands in full solidarity with Bulgaria.'
Since Russia's invasion of Ukraine in 2022, European countries have reported Russian drones
breaching their airspace multiple times and mines floating in the Black Sea across trade and energy routes
.