BUENOS AIRES, Argentina -- A court sentenced one of Argentina's most feared former military leaders to life in prison on Thursday for the 1977 kidnapping, torture and killing of four activists.

Luciano Benjamin Menendez, 81, was commander of the regional Third Army Corps in Cordoba five years during Argentina's 1976-1983 military dictatorship.

Menendez, who was already under house arrest for previous convictions related to the dictatorship's "dirty war" against leftists, will be transferred to a prison following Thursday's conviction.

Hundreds of people gathered outside the courtroom -- many holding placards and pictures of the alleged victims -- erupted into cheers upon hearing the verdict.

The verdict was symbolic both because of Menendez's gruesome reputation as controller of one of the dictatorship's worst torture centers and because he was ordered to serve the rest of his sentence in prison.

Many convicted former military officers are serving their sentences under house arrest, as dictated by an Argentine law that applies to those over 70 years old or of poor health.

Six other former military officers and one civilian were also convicted of the crimes Thursday and given sentences ranging from life in prison to 18 years. The trial began less than two months ago.

The four victims, Hilda Palacios, Humberto Brandalisis, Carlos Lajas and Raul Cardozo, were kidnapped in 1977.

According to prosecutors, they were taken to the prison and torture center known as La Perla, which was run by the Third Army Corps, and killed the next month. Their bodies were then dropped in the street to make it seem as if they had been killed in a shootout, before being collected by authorities.

Palacios was found in 2004 in a local cemetery. The bodies of the others have not been found.

Earlier this morning, Menendez read a prepared statement in front of live television cameras and a hostile crowd in which he justified the military regime's repression as necessary in the face of a leftist militant threat.

"We had to take appropriate measures," he said.

One of the judges interrupted Menendez's comments repeatedly to silence, and eventually eject, a vocal member of the crowd.

Menendez's is the latest in a series of convictions of "dirty war" suspects.

President Cristina Fernandez has prioritized human rights trials. In 2005, the Supreme Court struck down amnesty laws from the 1980s that had protected suspects from the dictatorship.

The others convicted on Thursday are Hermes Rodriguez, Jorge Acosta, Luis Manzanelli, Carlos Vega, Carlos Diaz, Oreste Padovan and Ricardo Ramon Lardone, a civilian who worked for military intelligence.

About 13,000 people were killed during the dictatorship, according to official numbers, but human rights groups claim the number is closer to 30,000.