Colombia's main leftist rebel group shot and killed four hostages held for more than a decade, President Juan Manuel Santos said Saturday, vowing to fight the rebels with everything in reach.

A fifth hostage, a policeman, was found alive, Defense Minister Juan Carlos Pinzon told reporters.

"This is yet another example of how brutal and cruel the FARC is. ... When faced with security forces, they (the rebels) had no qualms about killing them in cold blood," Santos said.

The Revolutionary Armed Forces of Colombia, known as FARC, has been at war with the Colombian government since the 1960s. While severely weakened in recent years, the guerrilla group has continued to carry out kidnappings and attack security forces.