Rioting broke out at the Fort Chaffee refugee relocation center tonight as Cubans pelted police and soldiers with rocks after climbing over the front gate. Between 15 and 20 law enforcement officers, one civilian and four refugees were hurt, authorities said.

The number of refugees involved was unclear, with reports ranging from about 200 to up to 1,000.

After the demonstrators got outside the gate, they tried to race up Arkansas Rte. 22 to nearby Baring, but were turned back by state troopers, who beat them with billy clubs. Several troopers swung their night-sticks like baseball bats, getting a good grip with both hands and swinging from the heels.

The Cubans responded by hurling rocks and chunks of concrete -- some six inches square -- at the troopers.

After being pinned down behind cars and trucks for about 10 minutes, troopers fired about 20 rounds with shotguns and pistols, forcing the refugees back into the sprawling Army base.

Three refugees were admitted to St. Edward Medical Center near the base with gunshot wounds, according to hospital spokesman Jim Hannah. A fourth refugee was admitted with a stab wound. Hannah said one civilian who was hit by a rock was treated at the emergency room, and that medical personnel treated several other persons at the base.

Federal police and soldiers from Fort Sill, Okla., used tear gas and clubs in an attempt to subdue the refugees once they were back inside.

Maj. Brian McWilliams said the refugees were "mostly roaming around and starting fires."

About 10 minutes after the refugees retreated inside, they piled small wooden guardhouses and barricades sawhorses in a street and set them ablaze. Two mess halls and some barracks were also set on fire. A base fire truck was called out.

Bill McAda of the Federal Emergency Management Agency denied reports that the refugees had taken over the base, but said bands of refugees were on the loose inside.

Some Cubans showed their support of federal authorities by helping to put out the fires and trying to round up their unruly countrymen. McWilliams said a number of Cubans were arrested, but he did not know how many.

More than 100 civilians were evaculated from the base, McAda said.

Gov. Bill Clinton placed the Arkansas National Guard on alert and asked the White House for more military aid. President Carter dispatched White House staffer Eugene Eidenberg and Tom Casey of the emergency management agency to Fort Chaffe tonight.

The base, where more than 18,000 Cubans await relocation, has been the scene of numerous demonstrations during the last week over the pace of processing.

The riot was the second incident of the day in which refugees burst out of the base. Army troops and police wielding nightsticks turned back about 300 refugees who escaped this afternoon. w

Tonight's uprising began when the refugees began marching down the main street of the base toward the gate, yelling "Libertad." While marching, the refugees crossed paths with a television crew and apparently became angered. The TV crew was forced to take refuge in a nearby building.

As the crowd began climbing over a 5-foot-high chain link gate, military police reportedly stood by and watched.

Outside the base, about 50 state troopers began moving parallel with the refugees, trying to keep them near the base's fence line and from crossing the highway.

The troopers reportedly were joined by Fort Smith and Sebastian County deputies in firing warning shots, but it was not clear tonight when and how the three refugees treated for wounds were injured.

When the shots were fired, the refugees began falling back toward the base, a retreat of about 300 yards. They climbed back over the base's fence and began to lob rocks from behind it.

A reporter for the Southwest Record-Times of Fort Smith reported seeing one refugee, who had become separated from the crowd, beaten by troopers carrying nightsticks.

In Barling, police and soldiers had their hands full trying to calm about 500 local residents, some of whom were armed with shotguns, pistols and clubs. They cursed the soldiers for not letting them help battle the Cubans.

Shortly before 11 p.m., police arrested six Barling residents and charged them with disorderly conduct. The six, hauled away in a paddy wagon, had refused to leave the streets as ordered by policemen. After the arrests, only about two dozen people could be seen in the town of about 3,000.

Troopers sealed off Fort Chaffee tonight, but a Knight-Ridder reporter who was allowed in to retrieve his car said traces of tear gas hovered above the ground.

The charred guard stands and buildings made for an eerie scene, he said. The base looked as if it had been through a major battle, he added.

The first breakout followed a rock-and-bottle-throwing incident that left three military policemen injured. Four other law enforcement officers were hurt Saturday night in a similar incident when refugees hurled rocks and bricks.

In today's first incident, between 50 and 100 of the refugees got to within 50 yards of the Barling city limits, less than one mile from Fort Chaffee, before they were stopped.