Colombia's lower house late on Monday backed a bill to regulate transitional justice under the nation's peace deal with Marxist FARC rebels, including special tribunals that will try guerrilla leaders for war crimes.

The bill, which was approved with some modifications, is considered the cornerstone of the peace agreement signed last year between the government and the FARC, known until recently as the Revolutionary Armed Forces of Colombia.

The special courts will mete out alternative sentences like landmine removal for ex-guerrilla leaders who are convicted of war crimes committed during the five-decade war. Under the peace deal, those convicted will not serve time in traditional jails.

The lower house made changes to the text agreed this month by the Senate, so it must now go for conciliation between the two chambers. Once there is agreement on alterations the bill will go to President Juan Manuel Santos to be signed into law.

"With this step, we move towards peace: transitional justice guarantees the rights of the victims and establishes the basis for the reconciliation of Colombians," Mr. Santos said on Twitter.

Congress had until the end of the month to approve the law using a court-approved "fast-track" mechanism to reduce the number of required debates in an effort to implement the peace accord as quickly as possible.

The FARC, now a political party known as the Revolutionary Alternative Common Force, has argued against any changes to the original agreement, including extradition for crimes committed after demobilization.

The law, which would also apply to members of the military who have been accused of atrocities, is part of the agreement that allowed more than 11,000 members of the FARC – combatants and others – to lay down their arms and enter politics.

With the modifications, the FARC will be able to participate in politics, but face the risk of losing benefits if they committed sexual abuse against minors. They can be also be extradited for crimes committed after the culmination of the peace process.

"We have achieved an agreement with teeth," said Rodrigo Lara, president of the lower house. "Any FARC member who commits another crime will immediately leave the special regime and go to the ordinary jurisdiction. Sexual crimes will not be protected."

The leader of the FARC, Rodrigo Londono, a presidential candidate for next year's election, has said any changes put at risk the implementation of the peace agreement.

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Under the agreement the FARC will have 10 guaranteed seats in Congress until 2026. The group has announced a slate of candidates for elections next year.

This story was reported by Reuters.