At least 20 anti-government fighters have been killed in Colombia after the military launched bombing raids against their camp in Narino province, near the border with Ecuador, according to the Colombian army.

The fighters belonged to the Revolutionary Armed Forces of Colombia (FARC), the country's largest guerrilla group, General Leonardo Barrero, a local military commander, said on Sunday.

He said the fighters belonged to the mobile Marshal Sucre column who had set up a base in the area. At least three separate guerrilla camps were bombed during the operation at dawn on Saturday.

The attack came as Colombian President Juan Manuel Santos warned FARC leaders on Sunday that they had less than a year to reach a negotiated end to Latin America's longest-running armed campaign.

"This has to be a process of months, rather than years. In other words, this should not last any longer than November next year at the latest," Santos said at an event in the Caribbean resort city of Cartagena.

The FARC, Latin America's oldest armed group, started talks formally with Bogota on October 18 in neutral Norway. The talks moved to Havana, Cuba, on November 19 and will resume this week.

It is a conflict that has dragged on for almost a half century, with some 600,000 dead, 15,000 missing and four million people domestically displaced.

Source: Agencies