(Reuters) -- The Colombian government and leftist FARC guerrillas agreed on Thursday to form a truth commission that would seek to shed light on atrocities once Latin America's longest war is over.

Negotiators reached agreement despite a recent escalation of violence that has threatened the country's peace talks, taking place in Cuba.

"The commission ... will begin to function after the signing of a final agreement and once the FARC have laid down their arms," read the agreement announced by representatives of Cuba and Norway, two countries sponsoring the talks.

"The government will commit to ... the clarification of the truth in all events from the conflict, including the most serious human rights violations," the agreement said.

The United States has backed Colombia with billions of dollars of military aid in a conflict fueled by the illegal drugs trade.

In addition to government troops and the Revolutionary Armed Forces of Colombia (FARC), the war has involved right-wing paramilitary groups, armed criminal gangs and the leftist rebels of the National Liberation Army (ELN).

The 11 commissioners, yet to be selected, are expected to complete the body's task within three years.

Fighting has continued in Colombia during the two-and-a-half years of talks in Havana, adding to a death toll estimated at 220,000. Millions more Colombians have been displaced during the 50-year-old conflict.

In March, Colombian President Juan Manuel Santos had agreed to halt aerial bombing in recognition of a unilateral cease-fire called by the FARC. But he ordered new air assaults in response to a rebel ground attack that killed 10 soldiers in April.

Since then three bombing raids in recent weeks have killed some 40 guerrillas, and the FARC has renewed offensive operations.

Government and rebel negotiators have reached partial accords on three of five agenda points: land reform, the political future of the FARC and an end to the illegal drugs trade. Still under discussion are victim reparations and the FARC's demobilization.

Should the two sides reach a comprehensive agreement, it would be submitted to the voters for ratification.