The Colombian government asked the United Nations High Commissioner for Human Rights to help investigate and the agency has agreed to assist, according to a statement published on the president's Web site.

The president said it seems "criminals" in camouflage attacked an Indian community with guns near a place where cocaine is grown.

The Colombian government has offered a reward of up to the equivalent of $50,000 for information leading to the capture of those responsible, the Colombian Ministry of Defense said in a statement. Investigators know little about the group that conducted the attack or its motive, the statement said.Uribe

In February, guerrillas with the Marxist Revolutionary Armed Forces of Colombia, better known as FARC, admitted that they killed several Indians they had accused of collaborating with the Colombian government, news outlets reported.

A FARC statement about the killings was posted then by the New Colombia News Agency and Caracol Radio's Web site.

Human-rights groups and a state governor in Colombia accused FARC of killing at least 27 Awa Indians in separate attacks in southwest Colombia in early to mid-February.

The statement said the guerrillas were not targeting indigenous populations but took the action "against people who independent of their race, religion, ethnicity, social condition etc. accepted money and put themselves at the service of the army in an area that is the object of military operations."