A former police detective suspected of being a member of a kidnaping ring has been killed by unidentified gunmen, officials here said today.

The victim, Edgar Sigfredo Perez Linares, is the third suspect in the kidnaping case to die in unusual circumstances.

According to officials, Perez Linares was shot in the throat as he drove in the western province of Santa Ana on Sunday. An anonymous caller told a newspaper that Linares had been "machine-gunned because he belonged to a band of kidnapers the whole world knows."

Later, officials confirmed that the victim was Linares, who had been at large since the ring was exposed last month. It is said to have included several military officers who allegedly abducted five wealthy Salvadorans for ransom totaling more than $3 million. The case has attracted attention because the military by tradition has been immune from punishment in criminal cases.

One of the suspects, Ramon Erasmo Oporto, was found hanged in his jail cell. Another, Moises Lopez Arriola, was shot to death, allegedly by a night watchman who thought he was a burglar.

A spokesman at the U.S. Embassy said American officials did not have enough information to know whether the three deaths were linked or if they would hamper prosecution of other suspects. "The United States Embassy is disappointed that three figures who were suspects have met with violent deaths since the first arrests in the kidnaping case," he said. "We feel they might very well have had valuable information that could have shed more light on the case."

In Oporto's case, police called the hanging a suicide, but several sources raised the possibility that Oporto "had some help." They said he could have been an important witness because he allegedly guarded a house where kidnaped victims were held.

Oporto was a brother-in-law of Lt. Rodolfo Lopez Sibrian, who has been charged in the case and was implicated in the 1981 slaying of two American labor advisers and a Salvadoran agrarian reform official.