Colombia's president has dismissed the country's head of armed forces after he verbally maligned prosecutors and suggested action be taken against them in audio recordings obtained by a local news magazine.

General Leonardo Barrero's phone conversation with a colonel, who was imprisoned over possible links to extrajudicial killings, was recorded by prosecutors investigating corruption by senior officers in allegedly inflated military contracts, Semana reported.

Barrero said such prosecutions were "a bunch of crap'' and suggested that he and others "organise a mafia'' to discredit the officials involved.

President Juan Manuel Santos made it clear that Barrero was being fired for 'disrespectful remarks' and not for corruption, although four generals were forcibly retired on Tuesday in connection with the contracts scandal.

Semana said hundreds of hours of audio recordings in its possession showed that senior military officers received kickbacks of up to 50 percent on deals, Reuters news agency reported.

In a statement on Tuesday, Barrero said: "After 39 years wearing the camouflage uniform with pride, serving the country, the Military Forces, and especially, the National Army, I leave with the tranquility and satisfaction of having acted according to the principles and values that govern military life."

Santos' defence minister later announced that General Juan Pablo Rodriguez would replace Barrero.

Army scandals

The corruption investigation that Semana reported on grew out of an investigation into extrajudicial killings, Jorge Perdomo, the number two official in the chief prosecutor's office, said on Monday, AP news agency reported.

Colombian soldiers, the vast majority enlisted men, have been convicted of nearly 900 extrajudicial killings, dressing victims in fatigues and falsely presenting them as rebels killed in combat.

The victims in the cases, known as "false positives," were mostly down-on-their luck men lured to their deaths with bogus job promises. They were killed to boost the body count of supposed rebels killed in Colombia's long-running conflict.

The killings occurred principally over the decade ending in 2008, when the scandal broke and 27 officers were fired, three of them generals. Santos was defence minister then.

Juan Carlos Pinzon, Colombia's defence minister, acknowledged on Monday that "administrative deficiencies" had been found in army aviation contracts.

Another scandal, prompted by revelations in Semana last month, put the Santos government on the defensive over allegations that an army intelligence unit was spying on his negotiating team at peace talks with FARC rebels in Havana, Cuba.

The negotiations, which began more than a year ago in Cuba, aim to put an end to the longest-running conflict in Latin America, which has left hundreds of thousands dead in over a half century.

Source: Al Jazeera and agencies