Six NATO vessels have been in the Black Sea since March 4 on invitation from Romania, Bulgaria and Turkey for planned maneuvers. The group includes USS Vicksburg, four frigates - Turkey's Turgut Reis, Italy's Aliseo, Canada's Fredericton and Romania's Regina Maria, as well as Germany's Spessart auxiliary ship. US Vice-Admiral Brad Williamson is in charge of the group. According to NATO’s press-service the drills are aimed at practising protection from air raids and from torpedo attacks by submarines. NATO warships are obliged to meet the conditions of the Monroe doctrine not to stay in the Black Sea basin longer than 21 days. The water displacement of NATO warships staying in the Black Sea should not exceed 45,000 tons. Most recent NATO Black Sea maneuvers in this TASS photo gallery.