El Salvador's leftist rebels Saturday returned 17 sophisticated anti-aircraft missiles of the 28 stolen from Nicaraguan army arsenals last year, rebel leaders said.

Eight Soviet-made missiles - four SAM-7 and four SAM-14 - were handed over to Nicaraguan government and army officials at the Mexican embassy in Managua Saturday. The eight missiles had not left Nicaraguan territory.Mexico has played a mediating role between the FMLN and the Salvadoran government.

Rebel Farabundo Marti National Liberation Front (FMLN) representatives at the embassy handover said another nine missiles were being returned to Nicaraguan officials Saturday in El Salvador.

The illegal arms deal was uncovered when Salvadoran armed forces found a spent missile canister after rebels fired at an air force plane. A serial number on the canister was used to trace the missile back to a shipment sold to the Sandinista army by the Soviet Union, the Salvadoran military said.

Last month three active Nicaraguan army officers and a cashiered army major admitted they took 28 surface-to-air missiles from army warehouses in October and handed them over to the FMLN.

The four men, who face military trial for the missile affair, said they gave the guerrillas the weapons out of solidarity with the FMLN.

The incident was an embarassment for the Nicaraguan government and army, which has publicly depoliticized its force but still remains strongly identified with the former ruling leftist Sandinista National Liberation Front.

The FMLN said the 11 remaining missiles of the 28 taken from the Nicaraguan army had been fired at Salvadoran air force planes and helicopters.