Colombia's military says rebels from the Revolutionary Armed Forces of Colombia - FARC - have ambushed a military unit, killing six soldiers.

A military spokesman says three rebels were killed in the return fire Saturday about 400 kilometers northwest of the capital, Bogota.

Last month, the Colombian government says it killed more than 30 FARC rebels in a bombing raid.

FARC has been at war with the Colombian government since the 1960s. Their numbers have dwindled over the years, but some analysts estimate the group has as many as 9,000 fighters.

FARC has been designated as a terrorist organization by Colombia, the United States and the European Union.