The women, arrested Monday at dawn, were the latest of dozens of protesters to break into the military training ground on Vieques. They were immediately detained.
When a Navy bus carrying the detainees left the camp, about 80 other protesters jumped in their cars and chased the bus, Police Sgt. Jose L. Velardo said.
Police escorting the bus called for reinforcements, who set up a roadblock.
"We had 20 to 25 cars following this bus," Velardo said. "Things were very tense."
Protesters claimed riot police threw retired schoolteacher Luz Legillu to the ground and pointed weapons at her. Velardo said Legillu, wife of a former Vieques mayor, complained to him but said he did not see the scuffle.
Velardo said the crowd dispersed after local police intervened.
He also said riot police reported that protesters threw motor oil at the bus and patrol cars. The riot police commander could not be reached for comment immediately.
The clash came as the Navy's USS Harry Truman battle group continued practicing. Jets began dropping dummy bombs on the firing range last week. Ships are expected to fire inert shells during exercises that could last through Aug. 24.
Anger over the Navy's presence flared in April 1999 after a jet dropped two bombs off target and killed a civilian guard on the range.
Protesters invaded the area for a year until federal agents removed them May 4. The Navy owns two-thirds of Vieques. Its bombing range is about 10 miles from the civilian sector and covers 900 acres on the eastern tip less than 3 percent of the island.
A Puerto Rican government report said exercises over 60 years had stunted the economy and harmed the environment.
The Navy denies any damage and says its live-fire training at Vieques is essential practice that saves lives in conflicts.
Under an agreement between President Clinton and the Puerto Rican government, the Navy resumed exercises with dummy munitions until a referendum is held. The Navy must pull out by May 2003 if residents vote to expel it.
Several May 4 protesters remain in jail. They have refused to post bail, saying they don't recognize the jurisdiction of federal courts in this U.S. commonwealth. Some were re-arrested in early July for failing to post bail.
To convince Vieques that it can be a good neighbor, the Navy recently launched an Internet site to answer criticisms about the impact bombing has had on the island's 9,400 civilians, who live in the middle third of the 21-mile-long island.
The Navy is transferring the island's western third, a former ammunition dump, to Puerto Rico, and is drafting plans to promote economic development on Vieques with $40 million allocated by Congress.
It also is paying fishermen wh are barred from their fishing grounds during exercises, hopes to improve medical care on Vieques and is refurbishing a pier for better ferry service to Puerto Rico, about 7 miles to the west, said Gordon.