PANAMA CITY, DEC. 5 -- Hundreds of U.S. Army troops disarmed and seized dozens of rebellious Panamanian police and their fugitive former police chief today after a tense muzzle-to-muzzle confrontation that threatened to explode into violence.

One Panamanian was killed and one was injured, according to U.S. officials. No U.S. casualties were reported.

The action came after more than 100 well-armed Panamanian police and their leader, retired Col. Eduardo Herrera Hassan, burst through two undermanned U.S. Army roadblocks as they began a march on the National Assembly to present a set of hastily drawn grievances.

Herrera, a former police chief who was charged with plotting against the government six weeks ago, made a daring helicopter escape from prison Tuesday afternoon and took over the national police headquarters shortly after midnight.

The U.S. intervention, which came at the request of Panamanian officials, aborted what could have been an explosive challenge to the struggling, U.S.-installed government of President Guillermo Endara. But it also underlined the fragility of Panama's infant democracy, and the extent to which it remains dependent on the presence of nearly 10,000 American troops.

More than 500 U.S. troops of Joint Task Force Panama surrounded the police headquarters before dawn today. They were standing guard about 9:45 a.m. when Herrera and his followers suddenly walked out with a throng of journalists. The column of khaki-clad rebels, bearing assault rifles and shotguns, at first overwhelmed the Americans, who were spread in a thin perimeter about 300 yards from the police headquarters.

A frantic U.S. Army radio operator, instructed by his superior officer to stop the rebels, scrambled backwards with a patrol of about 10 troops as he tried to explain the problem over his handset.

"Only way we can stop them, we're gonna have to use force, and we're way outgunned!" he said.

The Panamanians were finally halted when U.S. reinforcements rushed in, ordering the police to drop their weapons and to lie spread-eagled on the ground.

In the chaos, small groups of Herrera's police made their way around the U.S. troops on foot and in vans and pick-up trucks and into a slum neighborhood called Curundu. Herrera, leading the pack in a camouflaged jacket and a 9mm pistol at his hip, briefly disappeared before troops surrounded him and about 20 of his men on a side street. Scores of children and teenagers wandered through the fray.

U.S. Col. James Steele, commander of the Military Support Group, took Herrera into custody. Herrera and his men were then delivered to Panamanian authorities at a police station a few blocks away.

Before last year's U.S. invasion of Panama, Herrera, a former Panamanian ambassador to Israel, turned up in Miami and, according to U.S. sources, went on the CIA payroll to organize a coup against general Manuel Antonio Noriega. No such attempt was authorized, however, reportedly because the Senate Intelligence Committee rejected it.

Steele, as head of the U.S. military assistance group in El Salvador in 1984-6, was linked to Oliver L. North's operation supplying Nicaraguan contras in that period.

The U.S. Southern Command in Panama said in a statement that Herrera and his men had been "taken into custody by Panamanian authorities with U.S. assistance." But journalists saw no Panamanian police presence whatsoever except for those rebels under arrest.

Scattered shots were heard throughout the incident. One Panamanian officer was hit in the back of the neck and Panamanian witnesses said he had been shot by a U.S. soldier. Unconfirmed reports said the man later died, apparently the only fatality.

The episode raises questions about progress toward one of the goals of U.S. policy here since the invasion last December that overthrew Noriega: to convert Panama's notoriously corrupt, anti-democratic army into a lightly armed civilian police force that would uphold the constitutional government.

U.S. and Panamanian authorities have insisted that they are reforming the police force, even though its members largely are the same as those who formed the old defense force. But one diplomat acknowledged the evident difficulty of the task today: "You're starting at rock bottom with people who never had any police training at all. It was just, 'Give me a truncheon and a gun and I'll go beat and shoot people and make millions of dollars.' "

Herrera told reporters before his arrest that he had been eating dinner in jail about 5 p.m. Tuesday when three soldiers arrived by helicopter to free him. He said he had no advance knowledge of the mission, which he called "a commando operation."

Perhaps because of the unexpectedness of his liberty, Herrera offered a welter of confusing motives and demands during his 17 hours of freedom. At various points, the former police chief said he was protesting unemployment, reaffirming his patriotism, demanding better treatment for the police and fighting for an "authentic democracy."

Endara referred to the episode as a coup attempt, but Herrera denied to reporters he had any intention of overthrowing the government. Herrera was police chief from shortly after the U.S. invasion Dec. 20 until August, when he was forced to retire. Authorities said he had balked at the efforts to transform the defense force.

On Oct. 18, authorities announced they had broken up a conspiracy led by Herrera to topple the Endara government. He was out of the country at the time but returned a week later to surrender to authorities, deny the charges and denounce the government as a U.S.-backed puppet. He was charged the next day with plotting to destabilize the government and had been in the Naos island jail near the Pacific entrance to the Panama Canal until his escape Tuesday.