Two American free-lance journalists brought a $23.8 million civil suit yesterday in a Florida federal court against 30 persons said to be linked to Nicaragua's counterrevolutionary rebels, alleging that they had smuggled weapons and drugs and planned to assassinate a rival guerrilla leader.

The suit brought immediate, strong denials from many of the defendants named.

The suit was filed in the U.S. District Court for the Southern District of Florida by radio reporter and television cameraman Tony Avirgan and his wife, reporter Martha Honey, who live in Costa Rica. Avirgan was seriously wounded in a bombing attempt against guerrilla leader Eden Pastora in May 1984 at a press conference in a jungle camp in southern Nicaragua. Eight persons were killed in the bombing.

Among the defendants are Adolfo Calero, a top leader of the rebels, known as contras; retired Maj. Gen. John Singlaub, a fund-raiser for the contras; Tom Posey, head of an Alabama paramilitary group called Civilian-Military Assistance; Theodore Shackley, a former deputy director of the CIA, and retired Maj. Gen. Richard Secord, a former deputy assistant secretary of defense.

"I deny all allegations of wrongdoing," said Calero when the complaint was served on him at a Miami press conference held yesterday by contra leaders.

In a statement released in Washington, Singlaub blasted the suit as "transparently scurrilous, cynical and duplicitous."

Andy Messing, head of a conservative aid organization called the National Defense Council, who was also named in the suit, called the charges "laughable." Others named are in several different American states and Central American countries and could not be reached for comment yesterday afternoon.

Renewed congressional debate is expected in mid-June on an administration request for $100 million in aid for the contras. Opponents of the Nicaraguan rebels and some disillusioned supporters have leveled charges of corruption against contra leaders in recent months, but U.S. government investigators have not confirmed them.

The journalists are represented by attorney Daniel Sheehan of the Christic Institute, a liberal, church-funded law group.

The suit centers on allegations about the activities of John Hull, an American who owns a farm in northern Costa Rica near the Nicaraguan border. The suit charges that Hull joined forces with Cuban-American contra supporters Rene Corvo and Felipe Vidal to organize an anti-Sandinista guerrila force in Costa Rica, in violation of the U.S. Neutrality Act.

The suit charges that Hull and others were paid fees by Colombian drug dealers who refueled their planes on Hull's farm. Hull and others are said to have used the drug money to purchase weapons illegally in Miami for the rebels.

The suit alleges that Hull and others helped hire and assisted a Libyan who is alleged to have carried out the press conference bombing, which Pastora has blamed on the Nicaraguan government.

The suit also charges that Calero participated in several meetings in 1984 at which attempts to kill Pastora were planned. Pastora, a mercurial rebel leader who has been reluctant to join forces with Calero's coalition, recently surrendered to authorities in Costa Rica, where he is in custody pending a decision on his request for asylum.

Sheehan said in an interview that he will call witnesses who have said they attended a meeting in Calero's house in Miami in which a plot against Pastora was discussed.