Thousands of people opposed to the Navy using Vieques island as a target range gathered Monday outside the prison where 38 people are being held for trespassing during recent military exercises.

Police estimated at least 5,000 people gathered at the federal prison in suburban Guaynabo to hear speakers such as U.S. Rep. Charles Rangel of New York. Last week, Rangel criticized a federal judge in Puerto Rico for sentencing the Rev. Al Sharpton to 90 days in jail for his Vieques arrest on May 1.

Sharpton and three other New York politicians, who each received 40 days in jail in their hearing last week, were moved Friday to a prison in New York City.

The 38 in Puerto Rico are serving sentences that range from 40 days to four months. Critics have said the sentences are too harsh for the misdemeanor charge.

"This is an American issue and we're going to solve it," Rangel said before the crowd.

The Navy has used Vieques for exercises for six decades. Opposition grew after a civilian guard was killed on the range by two off-target bombs in 1999.

The Navy has denied claims that the exercises pose a health threat, and says the training is vital for national security.

Vieques residents will decide in a November referendum whether the Navy must leave by May 2003 or whether it can stay. If it is allowed to stay, it can resume using live ammunition, which it had stopped doing after the fatal accident.

High-profile protesters such as environmental lawyer Robert Kennedy Jr., actor Edward James Olmos and U.S. Rep. Luis Gutierrez of Illinois also were among the 180 people arrested for trespassing on Vieques to stall exercises. Their court dates have not yet been set.