Leftist rebels fighting the U.S.-backed government in El Salvador have engaged in "flagrant violations of international law" by summarily executing captured civilian opponents, according to a study conducted by the human rights group Americas Watch.

Americas Watch called upon the rebels, the Farabundo Marti National Liberation Front (FMLN), to "immediately renounce this practice, which has claimed the lives of several hundred victims since the early 1980s."

Guadelupe Gonzalez, Washington representative of the FMLN, said, "We just received the report and need to study it further before responding."

Americas Watch, which has repeatedly condemned human rights violations by both the government and the rebels, conducted the latest study to rebut FMLN claims that its executions were carried out in accordance with international law, according to Americas Watch research director Anne Manuel.

The study rejected the rebels' argument. "All the evidence they have given us and our own research indicates that they do not in any way approach" international law standards of due process, Manuel said. The study also reported that "in many cases, the FMLN dispensed with the formalities of a trial by summarily executing their victims assassination-style."

A March 13 announcement by the FMLN that it would no longer attack civilians was encouraging, the study said, but it was violated in at least one instance nine days later in the shooting after capture of the son-in-law of the commander of the Salvadoran Air Force.

Even if the rebels adhered to their new policy, Manuel said, "that wouldn't bring them into compliance {with international law} because the new policy does not forswear assassinations of military people or others not actively engaged in combat," only the killing of civilians.