Guatemalan police on Friday arrested a former military chief of staff in the mass killing of government opponents during the country's 36-year civil war, the highest-ranking official yet detained for massacres in the 1980s.

Retired Gen. Hector Mario Lopez, 81, was allegedly involved in about 200 massacres committed while he was chief of staff of the Guatemalan military between 1982 and 1983, said prosecutor Mynor Melgar. He faces charges of genocide and forced disappearance, a category of crime in which the victim has never been found.

The civil war that started in 1960 cost about 200,000 lives before the government signed peace accords with leftist rebels in 1996. Independent reports blame the armed forces for most of the deaths.

Lopez was arrested in Guatemala City. He is accused of directing a "scorched earth" campaign against mainly Mayan communities during the dictatorship of Gen. Efrain Rios Montt.

Rights activist Mario Minera welcomed the arrest of Lopez.

"This opens the possibility that there could be justice for hundreds of families, there could be a historical accounting to explain why the general populace and the Mayan Indians were victims," Minera said.

Rios Montt told a local radio station that he would be willing to face justice as well for the events of the early 1980s. However, Montt enjoys immunity from prosecution because he is currently serving a term as a congressman.

"It was a time of war, of guerrilla wars," Montt told the Emisoras Unidas station. "If there is no justice, there can be no talk of peace."

It was not possible to reach Lopez for comment and it was unclear if he had a lawyer.