BOGOTA, Colombia (AP) _ In an unusual act of contrition, right-wing militias in Colombia have apologized for dragging a wounded guerrilla from a Red Cross vehicle last week and executing her.

The apology from the United Self-Defense Forces of Colombia, an umbrella group for the country's militias, was contained in a letter faxed to the Red Cross in Bogota on Thursday.

``We accept our responsibility for this lamentable incident that put at risk the good work of the International Red Cross in Colombia,'' the letter said.

The Red Cross had no comment on the apology.

In its letter, the militia group conceded that on Sept. 22 three of its fighters stopped a Red Cross vehicle outside Apartado, a town near the Panamanian border.

The men then grabbed the wounded guerrilla, whom the Red Cross was taking to a hospital, and later killed her. She was a member of the leftist Revolutionary Armed Forces of Colombia, or FARC, the Red Cross said.

Apologies are rare in Colombia's brutal, 36-year civil war, which has left at least 35,000 people dead, most of them civilians.