Colombia's largest remaining rebel group has acknowledged its role in the murder of an indigenous leader in violation of a month-old cease-fire, and that's raising tensions in its peace talks with the government.

President Juan Manuel Santos' government on Monday condemned the murder of Aulio Isarama and demanded the National Liberation Army provide information to lead to the arrest of those responsible. It also called on the rebels to take steps to guarantee such incidents aren't repeated.

Isarama was killed last week on the reservation in the western state of Choco, where he was governor.

The rebel group accused Isarama of being an informant for military intelligence.

Peace talks with group began in February following an agreement with the much-larger Revolutionary Armed Forces of Colombia.