Military investigators have found evidence that U.S.-backed Nicaraguan rebels helped to stage a wave of killings and kidnapings in Honduras during the past four years in an apparent effort to break up a left-wing arms smuggling network aiding guerrillas in El Salvador, Honduran officials assert.

A still-secret report by a Honduran armed forces panel probing more than 200 killings and abductions in this Central American country has concluded that Nicaraguan guerrillas -- known as contras, or counterrevolutionaries -- were responsible for the disappearances of at least 18 Hondurans and possibly a larger number of Salvadorans here, high-ranking Honduran military sources said.

"Many of the disappeared persons were on missions for Nicaragua or Cuba," two nations suspected of helping to arrange the smuggling, a government source said.

The report was said to attribute other abuses to Honduran armed forces security personnel, Salvadoran left- and right-wing groups operating in Honduras and Nicaraguan government agents.

The report highlighted the extent to which Honduras has become an arena where Central America's numerous guerrilla, paramilitary and political movements have staged relatively low-level campaigns of violence. It is the only country in the region that borders all three nations with insurgencies: El Salvador, Nicaragua and Guatemala.

A Honduran who has direct knowledge of the support network inside Honduras for the guerrilla movement of El Salvador said that the majority of victims were people who had been helping the guerrillas. This Honduran, a self-described sympathizer with leftist causes, said the paramilitary groups had seriously damaged the Salvadoran guerrillas' support network in Honduras.

"The repression here is pretty selective," the source said.

Armed forces commander-in-chief Gen. Walter Lopez named the military inquiry panel in early June in response to public pressure to clear up the cases of killings and kidnapings. He said then that some results would be made public before the end of 1984, and a summary of the report was released Dec. 29.

The three-page summary provided few details, except to note that foreign groups may have been responsible for many of the abuses and to say that the investigation would continue until late March. Since then, officers have leaked a few more details.

The accounts offered the first indication that the Nicaraguan rebels used murder and kidnaping in Honduras as a way to disrupt arms supplies to El Salvador. The CIA funded the Nicaraguan guerrillas from December 1981 until late last spring in an effort that the U.S. government described as having the primary purpose of interdicting arms shipments to the Salvadoran rebels.

CIA personnel also helped to organize and advise the Nicaraguan rebels, leading Honduran human rights activists to suggest that U.S. personnel either were aware of the vigilante activities in Honduras or helped supervise them.

"It could be linked to U.S. policy. It's part of the doctrine of counterinsurgency," a prominent human rights activist said.

A U.S. Embassy spokesman said this afternoon that the United States was aware of the allegations of abuses by the anti-Sandinista guerrillas but had not seen "any evidence, officially or unofficially, that in fact the anti-Sandinistas were involved in such behavior."

Representatives of the largest Nicaraguan guerrilla group, called the Nicaraguan Democratic Force, were unavailable for comment here, apparently because of a desire to keep a low profile and thus avoid offending their Honduran hosts. The group's leader, Adolfo Calero, was quoted earlier this week as saying at his home in Miami that he was unaware of such killings or abductions and that his group would cooperate with the Honduran armed forces in investigating them.

The investigative panel also uncovered evidence that Salvadoran left-wing and right-wing groups and Nicaraguan government agents were responsible for some of the abuses, military sources said. But most attention has focused on the role of the Nicaraguan rebels and Honduran security forces.

From 1981 through 1984, politically motivated killings totaled 134 and "disappearances" or kidnapings totaled 123, according to Dr. Ramon Custodio, a physician who is president of the Committee for Defense of Human Rights in Honduras. The committee bases its data on accounts provided to it by family members or friends of the victims and by persons who witnessed the abductions or shootings.

The paramilitary activities have upset many Hondurans, who have been unaccustomed to this type of violence, which is familiar to their neighbors in El Salvador and Guatemala.

Human rights activists, media reports and some Honduran officials blamed Gen. Gustavo Alvarez, the former armed forces commander-in-chief, for stepping up the violence after he took charge of the military in 1981. Political killings jumped from one in 1980 to 42 in 1981, according to the human rights committee.

A barracks coup ousted Alvarez on March 31, 1984, and shortly afterward the new commander-in-chief, Gen. Lopez, publicly pledged to clear up the killings and disappearances.

Lopez was described as wanting to clean up the armed forces' image, but he was in a difficult position because some Honduran officers allegedly implicated in the cases remain on active duty. In particular, one major was reported to be in Tegucigalpa despite efforts to send him to a diplomatic post abroad.

Alvarez was a strong supporter of the Nicaraguan rebels, who have bases along the Nicaraguan border, but the government here has distanced itself from the guerrillas since Alvarez was ousted.

Custodio and other human rights activists cautioned that the armed forces panel might be using the Nicaraguan guerrillas as scapegoats for abuses committed by the Honduran security forces. They also said the political violence has continued even after Alvarez's departure, citing 20 abductions since March 31.

The most recent victim, former Communist Party activist Jose Eduardo Lopez, disappeared Dec. 23 in the city of San Pedro Sula, according to the human rights committee.

"We believed that with the departure of Alvarez this apparatus had been dismantled. It appears that the apparatus still exists," a prominent politician and jurist said.

It was unclear if the Nicaraguan rebels still were believed to be involved in the paramilitary groups. Human rights groups said that the Honduran military's Special Investigations department, set up by Alvarez, was responsible for most of the abuses attributed to Hondurans.