MANAGUA, NICARAGUA -- The recent arrest of two Salvadoran guerrillas with a truckload of weapons on the outskirts of Managua has raised questions about a continuing relationship between Nicaragua's revolutionary Sandinista party and El Salvador's Marxist-led Farabundo Marti National Liberation Front.

According to a communique issued July 21 by the Internal Affairs Ministry of the new government of President Violeta Chamorro, the two Salvadorans were caught July 16 at a police checkpoint set up on a highway south of the capital to collect unauthorized weapons from civilians. The statement said the two were carrying six rounds for a Soviet-designed shoulder-fired antitank weapon and 20 "82mm grenades" in a pickup truck.

The communique said the men, Jose Antonio Castro Chicas, 45, and Carlos Ernesto Salmeron Hernandez, 34, told police they belonged to the Farabundo Marti Front, known as the FMLN, which has been fighting successive Salvadoran governments for more than a decade.

The ministry made no mention of where the men acquired the weapons or where they were taking them. But it stressed that in accord with a Central American peace plan, the government would "not permit the use of national territory by insurgent groups to attack other states."

After Chamorro's opposition coalition scored a landslide victory in February, the Sandinistas turned over the reins of government in April, following nearly 11 years in power. But they have maintained effective control of the army and police through officers trained as party cadres.

The arrest is seen by some diplomats and Nicaraguan sources as the result of unexepected initiative by lower-level police. There has been no explanation of a five-day delay in announcing it.

The U.S. government has information that the Sandinistas "are still supplying the FMLN -- very carefully," a diplomat said, although no evidence of such a post-election supply line has been disclosed. He said the captured arms may have been en route "point to point" before shipment to El Salvador, or their transfer could have been part of an FMLN "restructuring" in Nicaragua -- with the guerrilla group moving to new safehouses and generally lowering its profile.

A European military attache said that although U.N. monitors are now deployed in Nicaragua and patrol the gulf between Nicaragua and El Salvador in small boats, this country's borders are still porous, especially the one with Honduras. "You can deduce that weapons smuggling is going on today," he said.

Spokesmen for the FMLN in Managua, interviewed by a Sandinista radio station, denied that the two arrested Salvadorans were members of the guerrilla organization and demanded that Nicaraguan authorities prove any such connection.

Internal Affairs Minister Carlos Hurtado declared in a July 24 press conference that both belonged to the FMLN and indicated extradition to El Salvador was under consideration.

Another official of Chamorro's government said one of the men earlier had been captured by the Salvadoran army and released in an exchange of prisoners with the FMLN. The man later spent a year in Cuba before coming to Nicaragua eight months ago, the official said.

He said that although the Chamorro government was allowing insurgent groups long resident in Nicaragua to keep offices here, there is mounting concern over "certain indications" of continued arms transfers. "This movement of arms is especially worrying because it is going on in the heart of the city," he said.

Frank Cesar, a spokesman for the Internal Affairs Ministry, said "we are now investigating the source and the destination" of the weapons confiscated from the two Salvadorans. There are "some leads," he said, but he declined to elaborate, commenting only that "these are things that are very delicate."

Sandinista involvement in arms deliveries to the Salvadoran rebels was exposed last year when two weapons-laden Nicaraguan planes went down in El Salvador during a major FMLN offensive. The planes, carrying anti-aircraft missiles and other materiel, were found to have taken off from an airstrip guarded by Sandinista troops at the Pacific beach resort of Montelimar.

In its final weeks in power before giving way to Chamorro on April 25, the Sandinista government of president Daniel Ortega quietly granted Nicaraguan citizenship to more than 300 Salvadorans, many of them members of the guerrilla movement who had long resided in Nicaragua.

A list of 319 naturalized Salvadorans was published in the Official Gazette in May. Among those given Nicaraguan citizenship were Mercedes del Carmen Letona, a guerrilla commander in the People's Revolutionary Army faction of the FMLN who has become one of the organization's main negotiators.