Colombia President Juan Manuel Santos Tuesday announced a shake-up in military leadership two days after a magazine exposed corruption among high level officials.

"I considered it appropriate and necessary to make a change at the head of the army," Santos declared solemnly in a speech aired on television.

Colombia's army has been in turmoil since weekly magazine Semana published revelations of senior officers getting kickbacks for certain military contracts. Top officers were also accused of trying to block judicial probes into abuses committed by soldiers.

The top official to lose his post, General Leonardo Barrero, the commander of Colombia's armed forces, was fired "not for corruption but for his disrespectful speech," the president said.

Barrero had called on officers to join forces "like a mafia" against the investigating judges, who he called "sons of bitches," according to Semana, which based its expose on hundreds of hours of tape recordings.

The magazine said the money earned from kickbacks was to be used to pay off detained soldiers so they would "keep their silence" in criminal investigations of so-called "false positives" -- the term used for hundreds of civilians killed by soldiers and later presented as rebels killed in combat.

After Barrero's remarks were revealed, he officially apologized. But Tuesday he was replaced by General Juan Pablo Rodriguez, a former head of special operations.

Santos also fired four other officials who "knew about the irregularities but failed to act," he said, adding it was necessary to "cut off the problem at its roots" in order to "protect our army."

Colombian Defense Minister Juan Carlos Pinzon on Monday acknowledged "administrative deficiencies" had been found in army aviation contracts.

Another scandal, sparked 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.

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.