The Bratstvo, or Brotherhood Party, issued a press release Monday saying its members had moved boats into positions blocking the exits from the port of Odessa, preventing NATO ships from participating in the Sea Breeze 2008 exercise, RIA Novosti reported.

The left-wing group said three of its boats were detained, but the others continued the "blocking operation."

"The NATO drill in Odessa is being accompanied by numerous protests by local residents. This demonstrates the public mood in Ukraine over the government's course toward early admission to the alliance," the news agency reported the group as saying.

Ukrainian politicians opposed to the government's moves to join NATO said during the run-up to Sea Breeze they would organize mass protests to disrupt the drills, and last week protesters set up a camp in western Crimea to picket the exercises, RIA Novosti said.