Drones hit two commercial ships in the Black Sea off the coast of Bulgaria on Tuesday, sinking one of the vessels, the government said.

Axar.az informs, citing Euronews, a search is under way for the missing crew, with what is reported to be the first attack on shipping in the NATO member's economic zone.

The crew of the sunken vessel are missing and those from the second ship have been rescued, public broadcaster BNR quoted Rumen Nikolov, head of rescue operations in Varna, as saying.

Bulgarian shipping news site Maritime.bg named the vessels as the Alfa Watan, which it said sank, and the Able, whose 18 crew abandoned ship after a fire broke out and were taken aboard the Bulgarian ferry Dioscuria, some of them injured.

The origin of the drones has not yet been established, it said.