NATO warships entered the Black Sea on Thursday for what the alliance said were long-planned exercises and routine visits to ports in Romania and Bulgaria.

The move is not linked to the tensions over Russia's invasion of Georgia, which lies on the eastern shore of the Black Sea, about 900 kilometers (550 miles) from the Romanian coast, said officials at NATO's military command in southern Belgium.

Three warships — from Spain, Germany and Poland — sailed into the Black Sea on Thursday. They are due to be joined by a U.S. frigate, the USS Taylor, later this week.

They are "conducting a pre-planned routine visit to the Black Sea region to interact and exercise with our NATO partners Romania and Bulgaria, which is an important feature of our routine planning," said Vice-Adm. Pim Bedet, deputy commander at allied maritime headquarters in Northwood, England.

However, the move risks increasing tensions with Russia which has deployed ships from its Black Sea fleet to the Georgian coast.

The NATO flotilla includes Spain's SPS Adm. Juan de Bourbon, Germany's FGS Luebeck and the Polish ship ORP General K Pulaski. Romanian and Bulgarian ships will join them for exercises during a three-week deployment which NATO says has been planned for over a year.