The violence occurred after a midnight Wednesday (0400 GMT Thursday) deadline passed for the Navy to officially withdraw from the land, which for 60 years has been used as a bombing and artillery range, and for amphibious landing exercises.

The Fish and Wildlife Service of the US Department of the Interior is now in charge of the land, and plans to develop a wildlife refuge there.

Witnesses said between 500 and 600 protesters, many with their faces covered, charged a fence around the Camp Garcia bombing range at Vieques when the deadline was reached.

Police superintendant Victor Rivera said officers were unable to make any arrests because the violence occurred within an area under federal jurisdiction.

Rivera said he was to meet with Interior Department officials to see how local police could protect the federal lands.

The violence marred what was expected to be a peaceful ceremony organized by Vieques residents who led an international protest campaign to force the Navy to stop using their land as a bombing range.

Campaigners said years of target practice had affected the health of the local population, giving them one of the highest cancer rates in Puerto Rico. The US Navy has denied the allegations, saying the evidence was inconclusive.

As fireworks were set off, protesters chanting "Vieques Yes, Navy No" burned vehicles that have been used by the Navy and destroyed several structures, police and witnesses said.

Puerto Rico Governor Sila Maria Calderon watched the violence unfold from a stage set up in front of the fence's main gate where the official ceremony was to be held.

"These people who are committing these acts of violence are violating the law and the spirit of what this fight was all about," she said. Many around her booed the comments.

Calderon also said the people of Vieques "have sacrificed themselves for decades" in their fight to get the bombing range land back, and called on all Puerto Ricans to "repudiate" the violent acts.

Protests against the US military exercises on the island, which has a population of about 9,000 people, had been increasing since 1999 when a stray bomb dropped by a US plane killed a Puerto Rican security guard.

President George W. Bush promised in 2001 that the Pentagon would withdraw from Vieques by May 2003.

Also in 2001, the movement for a Navy-free Vieques scored another victory when 68 percent of the islanders voted in a non-binding referendum for closing down the bombing range.

US civil rights leader Al Sharpton spent three months in prison in 2001 for trespassing on Navy property during one of the protests. He was to be one of the guests at the handover ceremony.

Just after midnight Wednesday (0400 GMT Thursday) the Navy Department released a terse statement saying that it had "transferred all real property on the eastern end of the island of Vieques, Puerto Rico, to the administrative jurisdiction of the Department of Interior."

It made no mention of the troubles.

The Navy, however, is responsible for cleaning up unexploded ordnance on the beaches, some which will be opened to the public.

SPACE.WIRE