The women were quickly detained by the security forces.

Fishermen and beachgoers were meanwhile warned that waters around the eastern half of the island were restricted as of Monday.

The Vieques range came to prominence in 1999 when two American bombs fell off target during an exercise and killed a Puerto Rican civilian guard.

Exercise shortened

Activists occupied the range for a year but agreed to leave the island on condition that the Navy cut back the number of exercises from some 180 days to 90 days a year and use limited ammunition and inert bombs.

Puerto Rican Governor Sila Calderon, whose election platform included a promise to force the American Navy to leave, says she supports a deal endorsed by President George W Bush, for the navy to leave by May 2003.

But the agreement is now under review following the terrorist attacks on the United States last September.

Hundreds of protesters periodically invaded the seaside bombing range last year, often forcing the Americans to stop the naval exercises.

But the protests eased off after the 11 September attacks.

On Sunday fewer than 100 activists participated in a demonstration, shouting slogans through a bullhorn in Spanish, such as: "Fuera la Marina!" - Navy get out!