BOGOTA, Colombia -- (AP) -- A resignation letter purportedly written by the chief of Colombia's right-wing paramilitary forces has appeared on the group's Internet site, raising questions about whether it was the work of hackers.

 The letter, signed by Carlos Castaño, chief of the United Self-Defense Forces of Colombia, or AUC, appears on the website in lieu of the group's usual home page.

 ``Companions of the cause, we in the AUC are `friends and respectful of the state's institutions.' This principle is inviolable: Respect it. I irrevocably renounce the authority you had granted me,'' the message says.

 The authenticity of the letter has not been confirmed.

 The style of the missive is uncharacteristic of Castaño, who normally posts long messages on the site, including letters denouncing President Andrés Pastrana's peace
 initiatives with leftist rebels.

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