Eleven crew members are missing after a merchant ship sank overnight following a Black Sea drone attack, according to local officials.
Ukraine has directly blamed Russia for the latest attacks. European Commission President Ursula von der Leyen stated on Tuesday that the Black Sea is becoming another front of escalation in the Russian war in Ukraine.
The incident occurred a week after two other commercial ships were hit by sea and aerial drones in Bulgaria's economic zone.
Bulgarian media quoted Russian ambassador Mitrofanova as telling Radev that she had no information from Russia's defence ministry regarding the latest attacks.
Bulgaria is a NATO member. Radev, who came to office during the summer and has rejected suggestions that he is pro-Russian, also spoke to NATO Secretary General Mark Rutte about the attacks.