MEDELLIN, Colombia, June 1 (Reuters) - Ecuador on Sunday asked the Organization of American States to investigate claims by neighboring Colombia that linked Ecuador to left-wing rebels branded terrorists by Washington.

Ecuador denies the claims and asked the OAS to clarify the situation, which has increased tensions between the two countries since a Colombian military raid on Ecuador's side of the border in March killed top Colombian rebel Raul Reyes.

"Ecuador is officially asking the secretary-general of the OAS to launch an investigation," Ecuadorean Foreign Minister Maria Isabel Salvador told reporters on the sidelines of an OAS meeting in Medellin, Colombia.

Colombian and U.S. officials say files found on Reyes' computer indicate Venezuela's President Hugh Chavez and Ecuadorean leader Rafael Correa provided financial support or backing to the rebels. Both leaders deny those charges.

OAS chief Jose Miguel Insulza has said he is willing to look into the matter if a member country requests an investigation.

Interpol last month said its forensic tests showed the authenticity of the files but the international police agency could not vouch for the veracity of the contents of the computers found at Reyes' camp inside Ecuador.

Colombian President Alvaro Uribe is Washington's closest ally in the region while Correa and Chavez are fierce critics of the White House.

Colombia's four-decade-old guerrilla war often spills over into the neighboring countries. (Reporting by Nelson Bocanegra; Writing by Hugh Bronstein; Editing by Bill Trott)

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