Colombian authorities say nine police officers have been killed in an ambush by guerrillas from Colombia's second-largest rebel group, the National Liberation Army.

Authorities say three police officers were also wounded in Tuesday's ambush in the northwest province of Choco.

Police say the officers were investigating reports of suspicious activity by a group of armed men when the officers came under fire.

Officials also say about 100 members of the ELN took part in the ambush.

Separately, authorities say suspected members of the country's largest rebel group, the Revolutionary Armed Forces of Colombia, killed a police officer at a roadblock along a highway in the Ibague area, south of Bogota.

The ELN and FARC are fighting in a long-running civil war that also involves rightist paramilitaries and Colombia's government. The conflict leaves thousands dead each year.

Some information for this report provided by AP, AFP and Reuters.