The sound of gunfire and the roar of jets on practice bombing runs returned to the island of Vieques yesterday as the Navy resumed training exercises over the objections of the Puerto Rican government and protesters who briefly forced a halt to the bombing by sneaking onto a nearby island.

The exercise, using inert or "dummy" bombs, began about 9 a.m. when three Navy A-4 fighter jets swooped over the target range on the island's eastern tip and dropped several 25-pound bombs, according to a Navy spokesman, Lt. Jeff Gordon.

But a short time later, the exercise was suspended for about an hour when eight protesters were spotted on Yayi Key, a small island a little more than 200 yards northwest of the bombing range. Gordon said they were arrested by U.S. marshals and removed from the island.

About an hour later, two destroyers, the USS Ramage and the USS Peterson, began firing 70-pound inert shells from their five-inch guns into the bombing range, Gordon said. He said the shelling was expected to continue into the night.

Yesterday's confrontation was a continuation of a long-running, emotional dispute over the Vieques bombing range, which the Navy maintains is vital in providing its sea, air and Marine land forces with realistic training. The Navy has used the range for almost 60 years, and it has long been a source of resentment to Puerto Rican residents. That resentment boiled over in April 1999, when David Sanes Rodriguez, a civilian security guard working for the Navy, was killed by two errant bombs dropped by a Marine F-18 fighter jet.

The practice bombing is expected to intensify early next week. A 12-ship battle group headed by the aircraft carrier USS Enterprise, scheduled to arrive off Vieques today, likely will begin several days of training on Monday, Navy officials said. The battle group, which includes about 15,000 sailors and Marines, is on its way to the Persian Gulf to relieve another battle group led by the carrier USS Harry S. Truman.

The resumption of practice bombing set off emotional protests on Puerto Rico's main island and nearby Vieques, which is just east of the main island. Shortly after midnight, about 400 people who traveled by car caravan from San Juan and then boarded a ferry for Vieques arrived on the island to the chant of "Navy out."

Gordon said early yesterday afternoon that protesters threw an incendiary device onto Navy property on the island, setting a brush fire, and hurled a rock at a Navy vehicle, shattering the windshield. Early yesterday afternoon, 49 protesters broke down a fence that had been erected about 100 yards from the main gate of Camp Garcia, the Navy installation on Vieques, Gordon said. He said they were detained by Navy security personnel and later arrested by U.S. marshals.

"We are disappointed that they allowed the protesters to cut the fence and enter Navy property in plain view without doing anything about it," Gordon said of Puerto Rican police assigned to provide security outside the installation.

Sila Maria Calderon made expelling the Navy from Vieques a centerpiece of her campaign for governor last year and has pressed the issue since taking office in January. Calderon and other Navy critics maintain that the training exercises are damaging the health of the island's 9,300 residents and the environment.

Calderon pushed anti-noise legislation through the Puerto Rican legislature earlier this week and used the measure as the basis for a lawsuit in federal court seeking to stop the training exercise. But a judge, while suggesting that the Navy should postpone the practice bombing until a review of medical studies on its effects is completed, rejected an emergency request to block the exercise.

Calderon is a member of the Popular Democratic Party and an opponent of statehood for Puerto Rico, a U.S. territory. Gordon, the Navy spokesman, charged that the issue is also being exploited by Puerto Rican nationalists who favor independence for the commonwealth. He said that more than 90 percent of the about 500 people who have been detained on Navy property during protests since the 1999 accident were not Vieques residents but members of the Puerto Rican Independence Party.

The issue has also attracted attention from U.S. politicians, especially in New York, which has a large Puerto Rican population. Sen. Hillary Rodham Clinton (D-N.Y.) has spoken out against the bombing, as has New York Gov. George E. Pataki (R), who recently visited Vieques.

Protesters occupied the bombing range for more than a year after the 1999 accident but were ejected by U.S. marshals last May. This is the fifth training exercise the Navy has conducted on Vieques since then, but all have used inert -- not live -- ammunition. In January 2000, the Clinton administration reached an accord with Calderon's predecessor, Pedro Rossello, that calls for a referendum by Vieques residents in November to force the Navy to leave the island by May 2003 or allow it to resume live bombing. If the Navy prevails, the United States had pledged $40 million in economic aid to Puerto Rico.

Yesterday's protests on Vieques were nonviolent. The group that penetrated the fence near the entrance to the Navy installation quickly dropped to the ground to signal nonresistance to Navy authorities or held out their arms to be handcuffed.

"Peace for Vieques," some screamed as Gospel music played.

There was also an uneventful protest against the resumption of the bombing in front of the White House as about 40 demonstrators carried signs and shouted slogans in English and Spanish.

Staff writer David Fahrenthold in Washington and special correspondent Laura Albertelli in Vieques contributed to this report.

Outside main gate of Camp Garcia on Vieques Island, the Rev. Wilfredo Estrada urges demonstrators from Puerto Rico to maintain calm during their march against Navy's use of the island for training exercises with inert and live ammunition. Practice bombing resumed yesterday.