Protesters sneaked onto the U.S. Navy's prized firing range on Vieques island and put themselves in the line of fire, forcing a three-hour delay before shelling began Saturday in a second day of military exercises.

Five protesters were detained inside the target zone overnight and three more were found after daybreak, spokesman Lt. Corey Barker told The Associated Press.

Shelling from ship to shore, with non-explosive ammunition, began just after 11 a.m., the Navy said, three hours behind schedule.

Navy spokesman Jeff Gordon said officials were confident the target area was cleared of protesters before the shelling began, but protest leaders insisted they still had people on the range.

In one close call Friday, fighter jets began the exercises by dropping nine dummy bombs before eight protesters were spotted on an island within 100 yards of the target zone, Gordon said.

The latest detentions brought to 55 the number of protesters arrested since Thursday night, when people began breaching the restricted military zone on the outlying island to prevent the first Navy exercises since December.

Among the arrests announced Saturday was local Sen. Norma Burgos, a longtime proponent of U.S. statehood for Puerto Rico.

At least three people were injured in violent confrontations. Those arrested will be prosecuted for trespassing on federal property, the Navy said.

Gordon said the exercises "have been hindered very little" by the intruders.

But it appeared a partial victory for demonstrators who believe the military activity harms islanders' health and the environment.

The Navy insists it does not hurt the island's 9,400 residents and says local studies that show higher rates of cancer and infant mortality are unscientific and biased.

The military exercises have stirred up anti-U.S. sentiment on Puerto Rico, a U.S. territory where residents cannot vote for president and pay no federal taxes.

On the edge of the restricted military zone, sailors laid down new razor wire and repaired some of the gaps that protesters cut in chain-link fences in more than a dozen places Friday.

Some demonstrators hurled rocks and cow manure at federal authorities over a trampled section of fence on Friday. The authorities fired rubber bullets and pepper spray at demonstrators, and a Roman Catholic priest was lightly injured when he was hit in the abdomen by a rubber bullet.

One sailor was hit in the head by a rock, the Navy said.

Navy security guard Luis Sanchez said that although demonstrators speak of "Peace for Vieques," their actions don't match.

"That isn't peaceful. That's a war," Sanchez said.

The exercises began after a federal judge rejected a last-minute legal complaint by the Puerto Rican government, which argued the exercises would harm islanders and violate a new local law on noise pollution. The government said it would appeal.

In a decision that could lessen tension, the Navy announced it would suspend exercises for one day Sunday to honor the beatification of Carlos Manuel Rodriguez Santiago in Rome. Rodriguez, a layman who died in 1963, will be the first Puerto Rican beatified, a step before sainthood.

The Navy exercises involve about 15,000 sailors and Marines and a dozen cruisers and destroyers in the battle group led by the Norfolk, Va.-based aircraft carrier USS Enterprise.

Among protesters who may remain in the restricted area is Myrta Sanes, sister of civilian security guard David Sanes, whose April 1999 death by bombs dropped off-target on the range provoked public anger.

After the guard's death, protesters occupied the range and prevented exercises until they were removed by U.S. marshals in May 2000. Since then, training has been limited to inert ammunition.

Actor Edward James Olmos arrived on Vieques Friday night and added his voice to the protest: "(The Navy) should take everything they are doing here to the United States," Olmos told 300 cheering protesters.

Olmos was accompanied by environmental lawyer Robert F. Kennedy Jr., who said he had asked Olmos to come so the two could "get arrested."

In New York City, which has a large Puerto Rican population, Gov. George Pataki denounced the exercises during a news conference Friday. He pledged to lobby the federal government to pull the Navy out of Vieques.