Kiev - Ten Communist rowboats blocked the exit of a squadron of NATO warships from a Ukrainian harbour, Channel 5 television reported Monday.

Demonstrators manning the craft had set up a patrol line in Odessa bay between the vessels and the open Black Sea, preventing NATO combat vessels from departing to participate in the US-led Sea Breeze 2008 international naval exercise.

Port officials had taken three boats into custody by mid-morning, but the blockade was continuing as Ukrainian police attempted to convince the protestors to move out of the way.

The anti-NATO activists were members of three extreme left-wing groups opposed to Ukrainian cooperation with the Western alliance.

"The remaining seven boats are heroically continuing their blockade (of Odessa port and the NATO warships)," a statement from the nationalist Bratsvo group claimed.

The Sea Breeze maneuvers practicing peacekeeping operations had been scheduled to begin on Monday.

The multi-national naval exercise, scheduled to take place from July 14 to 26, includes warships from the US, Belgium, Germany, Turkey, Latvia, Denmark, Canada, and Greece; as well as non-NATO members Macedonia, Georgia, and Ukraine.

More than 1,000 NATO ground troops, 30 warships, and dozens maritime helicopters and aircraft will practice landings and ship-to-shore operations.

Ukraine's contribution to the training is the largest in the 11-year history of the exercises and includes 15 warships, four planes, ten helicopters, and 500 soldiers and sailors.

NATO has helped the Ukrainians participate in the annual naval exercises by providing money to help Kiev pay for fuel and food for its cash-strapped military.

Ukraine's pro-West government strongly favours membership in NATO, despite a luke-warm to antagonistic attitude towards the alliance by most Ukrainians.

Some 200 anti-NATO demonstrators gathered near the House of Officers building in Odessa carrying signs saying, among other comments, "NATO is worse than Gestapo!," "Ukraine and Russia - Brothers!," and "Odessa will not invite NATO into its house!"

Russian officials have spoken out against the Sea Breeze training, arguing that intensified Ukrainian association with NATO is threatens Russian national security.

Ukrainian officials have alleged that local left-wing groups routinely protesting Ukraine-NATO training are funded by the Kremlin, a charge denied by Moscow. (dpa)