18 leftist rebels killed in raid on Western Colombia guerrilla camp

Colombia’s President Juan Manuel Santos announces that at least 26 leftist rebels have been killed in a raid in western Colombia, as he's flanked by Defense Minister Juan Carlos Pinzon, left, and Armed Forces Commander Gen. Juan Pablo Rodriguez, at the presidential palace in Bogota, Friday, May 22, 2015. Colombia's largest rebel group, the Revolutionary Armed Forces of Colombia (FARC), announced they're ending a unilateral cease-fire in response to the military raid on their guerrilla camp. (AP Photo/Fernando Vergara) (The Associated Press)

Colombia’s President Juan Manuel Santos announces that at least 26 leftist rebels have been killed in a raid in western Colombia, as he's accompanied by Navy Commander Adm. Hernando Wills, left, Defense Minister Juan Carlos Pinzon, second from left, Armed Forces Commander Gen. Juan Pablo Rodriguez, second from right, and National Police Chief Gen. Rodolfo Palomino, right, at the presidential palace in Bogota, Friday, May 22, 2015. Colombia's largest rebel group, the Revolutionary Armed Forces of Colombia (FARC), announced they're ending a unilateral cease-fire in response to the military raid on their guerrilla camp. (AP Photo/Fernando Vergara) (The Associated Press)

Ivan Marquez, chief negotiator for the Revolutionary Armed Forces of Colombia, left, arrives for a new round of peace talks with Colombia's government, accompanied by fellow FARC delegates Pastor Alape, right, and Carlos Antonio Lozada, center back, in Havana, Cuba, Thursday, May 21, 2015. (AP Photo/Desmond Boylan) (The Associated Press)

Officials say that at least 18 leftist rebels have been killed in a raid in western Colombia.

A military official says the operation in Cauca province was carried against the 29th Front of the Revolutionary Armed Forces of Colombia on Thursday. The official spoke on condition of anonymity because he was not authorized to comment publicly.

President Juan Manuel Santos is expected to provide details early Friday.

The attack is the biggest blow against the FARC since Santos' government resumed air raids on guerrilla camps in April following a rebel attack that left 10 soldiers dead.

A rebel leader known by his alias as Pastor Alape issued a Twitter post calling Thursday's raid a cold-blooded murder in the dead of night.