Uruguay's last military dictator, Gregorio Alvarez, was charged with the forced disappearance of political prisoners and sent to a military prison on Monday, a prosecutor said.

Alvarez, an 82-year-old retired army general, led Uruguay from 1982 until 1985, shortly before the restoration of Uruguayan democracy.

Judge Luis Charles charged Alvarez in connection with the disappearance of some 40 Uruguayan political prisoners who were seized by military rulers in neighboring Argentina and then were transferred secretly to Uruguay between 1977 and 1978, prosecutor Mirtha Guianze said.

Charles had no comment on Monday's closed proceeding.

Guianze has argued that Alvarez was in a position to know about the illegal crackdown on dissidents, both as former army commander-in-chief and later de facto president.

Alvarez said in earlier court appearance that he knew nothing of illegal abductions and forced disappearances. But courts rejected his efforts to challenge the constitutionality of the investigation.

Prosecutors say Uruguayan political prisoners were brought in from Argentina in a secret airlift as part of "Plan Condor," in which South America's right-wing military regimes cooperated to crush leftist dissent.

The military ruled Uruguay between 1973 and 1985. Argentina was under military dictatorship from 1976 until 1983.

Some 150 Uruguayan activists, believed to have been seized by governments of the era, remain missing. Argentines are still seeking information about nearly 13,000 officially listed as dead or missing from the period of military rule.