The FARC guerrilla group for the first time accepted partial responsibility Tuesday for the thousands of victims of Colombia's nearly 50-year-old insurgency.

The statement was read out by a top FARC negotiator on the sidelines of peace negotiations in Havana between the leftist rebel group and the government of President Juan Manuel Santos.

"Without a doubt, there has also been cruelty and pain provoked by our forces," said the negotiator, Pablo Catatumbo.

"Still, we must recognize the need to approach the issue of victims, their identification and reparations with complete loyalty to the cause of peace and reconciliation," he said.

The acknowledgement that the FARC bears partial responsibility for the bloodshed comes nearly a month after Santos publicly admitted that the Colombian state was responsible for "serious violations" of human rights during the conflict.

Taken together, the statements appeared to mark a significant step forward in the peace process, which has been underway since November.

Colombia's constitutional court is expected to rule soon on a proposed legal framework for dealing with issues of accountability during a transition to peace.

Catatumbo called anew for the creation of an international "truth" commission to investigate the "fratricidal conflict" in Colombia.

"This commission in our opinion should be formed immediately," he said, calling on "the entire country to hold a day of reflection and contrition."

A government commission last month estimated that some 220,000 people have lost their lives in Latin America's oldest armed conflict. Other estimates rise as high as 600,000.

The peace talks in Havana have yet to take up the issue of reparations for the victims. Other pending agenda issues are the laying down of arms and drug trafficking.

The two sides currently are discussing the question of the FARC's participation in politics, and in May negotiators reached a consensus on the complex issue of land holdings.