Ten retired members of Colombia's military began admitting to victims' families on Tuesday their roles in the assassination of 120 civilians that were later presented as rebels killed in combat.

It was the first public admission by the former soldiers that they had made people disappear before killing them in cold blood in the mid-2000s.

One general, four colonels and five officers, as well as a civilian, were due to make their confessions to the special tribunal set up as part of the 2016 peace deal that ended a half century of conflict between the government and Revolutionary Armed Forces of Colombia (FARC) rebels.

The "false positives" scandal, in which murdered civilians were passed off as enemy combattants, is the largest ever to have rocked Colombia's armed forces.

"They were rural workers, not subversives, guerrillas and thugs as they were branded," said Eduvina Becerra, the partner of a murdered farmer. "I ask you to clear our family names," she said.

Around 50 of the victims' family members showed up to the Special Jurisdiction for Peace (JEP) hearing in the northern city of Ocana, as the soldiers gave details about how they murdered their victims, most of whom were men aged 25 to 35.

"I acknowledge and accept my responsibility as co-perpetrator" of the murders that took place between 2007 and 2008, said Nestor Gutierrez, a former non-commissioned officer in the army.

"We murdered innocent people, peasants," he said.

The JEP, which was set up in 2017 to try the worst atrocities committed during the conflict, said a battalion stationed in Ocana tried to inflate their successes in combating guerrillas and other armed groups, motivated by "the army's institutional policy of counting bodies."

According to the tribunal, more than 6,400 civilians were murdered between 2002 and 2008 after being lured to areas far from their homes.

(With input from AFP)