PANAMA CITY, MARCH 1 -- A strike to protest the rule of Panamanian military strongman Gen. Manuel Antonio Noriega gathered strength today despite signs of an intensified crackdown by security forces on its proponents.

The strike, in its second day, paralyzed much of the capital, shutting shopping centers, gas stations, supermarkets, financial institutions and industries. Diplomats estimated that the strike halted 75 percent of the capital's economic activity, and organizers said they planned to continue it at least through Wednesday.

The main organizing group, the National Civic Crusade, put the strike's effectiveness at 85 percent. The vital banking sector, the biggest in the region, was effectively closed as bank employees stayed away.

The Panama Canal operated normally today, a spokesman for the U.S.-run Panama Canal Commission said. But there were indications of sympathy for the strike among some of the canal's 7,400 workers as the head of the commission issued a stern warning against any interruption.

Faced with the spread of the general strike, the 15,000-member Panama Defense Forces commanded by Noriega deployed additional units around the city.

In a move apparently intended to suppress information about the strike, government agents in civilian clothes broke into Radio Mundial and arrested the owner, Carlos Zuniga, and at least five other persons. They were beaten and later released, Zuniga told the press.

Residents of the area responded by setting up barriers in the streets and hurling rocks at the agents, who fired in the air as they tried to take their prisoners away.

The rock barrage kept the security men bottled up in the radio station for about 30 minutes until riot police known as "the Dobermans" arrived to rescue the plainclothesmen, who were identified by witnesses as members of the Defense Forces' military intelligence branch. The riot police fired birdshot at the protesters, slightly injuring one woman.

Witnesses said four detainees from the radio station tried to flee their captors. One ran away and three were quickly recaptured, shoved into cars and driven away at high speed. One government agent was reported hit by a car driven by a colleague.

At one point, plainclothesmen at the scene held a pistol to the head of a Tampa Tribune photographer, Allyn DiVito, and demanded his film.

"We don't have anything to fight with against these people," said a witness, university professor Gonzalo Cordoba, as he watched riot police guard the area after the incident. "The United States created this monster {Noriega} and now they're telling us we have to get rid of him, and we can't." Radio Mundial, the last independent radio station broadcasting news of opposition activities, was airing an appeal to maintain the strike by a member of the anti-Noriega National Civic Crusade when the raid occurred.

Other opposition news media have been shut down one after another since Noriega was indicted on drug-trafficking and racketeering charges by two U.S. federal grand juries in early February.

At the time of the raid, the acting president installed by the Noriega forces on Friday was pledging in a state-of-the-union speech to "respect the freedom of all citizens to organize and express themselves."

At the opening of the National Assembly, Manuel Solis Palma, who was named "minister in charge of the presidency" when the military ousted figurehead president Eric Arturo Delvalle for trying to fire Noriega, said Noriega "has been the victim of one of the most violent and long-running slander and defamation campaigns that any leader has ever suffered."

Delvalle remained in hiding for a third day to avoid deportation.