Gen. Gregorio Álvarez arrives at court for his trial in Montevideo, Uruguay, in 2007. (Andres Stapff/Reuters)

Gen. Gregorio Álvarez, the last leader of Uruguay’s brutal dictatorship of the 1970s and 1980s, died Dec. 28 while serving a sentence for human rights abuses. He was 91.

The military’s health service said he died at the Central Hospital of the Armed Forces in the capital city of Montevideo.

Under Gen. Álvarez, Uruguay was part of the secret alliance of South American dictatorships known as Operation Condor, in which military leaders cooperated in persecuting and killing one another’s dissidents.

Gen. Álvarez, whose father was also a general, participated in the 1973 coup that dissolved the congress following a government crackdown on the Marxist Tupamaro rebels, who were trying to seize power by force. One of Gen. Álvarez’s brothers was killed by Tupamaro attackers in 1972.

Gen. Álvarez became army chief in 1978 and took over the presidency in 1981. His government imprisoned democratic critics and censored the press.

Gen. Álvarez agreed to hand over power to an elected civilian government in 1984 as the wave of dictatorships in the region was starting to recede. Argentina’s military rule ended a year earlier, Brazil’s a year later.

Hundreds of suspected leftists were arrested and tortured during the dictatorship, and historians say an estimated 180 Uruguayans were killed — most of them while in the custody of the government’s Argentine allies.

In 2009, Gen. Álvarez was sentenced to 25 years in prison for his responsibility in the death or disappearance of 37 Uruguayans under Operation Condor.

During his trial, he said he knew nothing of illegal abductions and forced disappearances.

Prosecutors argued that Gen. Álvarez was in a position to know what happened to the political prisoners as army commander in chief and later as de facto president.

—Associated Press