Seven NATO countries completed naval exercises in the Black Sea on Thursday, officials said, according to Reuters.

Led by the Bulgarian navy, the 10-day drills aimed to improve tactical coordination of allied units "in a multi-threat environment," NATO has said.

Vessels took part from Bulgaria, Romania, Turkey, Greece, Italy, Britain and the United States.

"The navy exercises BREEZE 2014 successfully concluded," a Bulgarian defense ministry spokesman said.

The Romanian Navy said exercises involved commercial traffic monitoring, reaction to asymmetric threat warnings, anti-submarine warfare and artillery firing.