Retired Colombian Gen. Rito Alejo del Rio was convicted Friday and sentenced to nearly 26 years in prison for the 1997 murder of a peasant leader in a joint army-paramilitary operation.

A judge found Del Rio to be "co-responsible" for the killing of peasant Marino Lopez Mena during Operation Genesis, launched by the army's 17th Brigade in the conflictive northwestern region of Uraba.

Several paramilitary commanders had implicated Del Rio in the slaying.

Lopez Mena, a black peasant leader, was killed and dismembered in February 1997, in Bijao - one of 23 communities located in the Cacarica River basin - by men from the Elmer Cardenas Bloc of the now-defunct AUC federation of rightist militias.

Demobilized members of that bloc, including its former commander Freddy Rendon Herrera, confessed to the murder and testified to the complicity of the then-military chief of that region.

Del Rio was regarded in some sectors as the "pacifier" of Uraba, but his offensives were marked by killings of innocent civilians and forced displacements of entire communities.

According to prosecutors, "a macabre alliance" was formed between the AUC and the army in that region against leftist guerrillas "without regard for the civilian population."

Del Rio has been held at a military facility in Bogota since his arrest in September 2008.

More than 31,000 AUC fighters demobilized between 2003 and 2006 as part of a peace process that included a promise of lenient treatment for paramilitaries who made full confessions and offered some form of restitution to victims.

Colombian prosecutors have linked the AUC to more than 20,000 murders. EFE