Colombia's president has announced the deaths of nine rebel fighters in an aerial bombing raid by the Colombian army and in clashes with troops in a southeastern jungle region.

The operation on Monday, which military and police sources said involved the use of jets and helicopters, took place in Meta province, a vast area believed to have significant oil resources and where members of the Revolutionary Armed Forces of Colombia (FARC) maintain a heavy presence.

"Military forces and police in Meta take down nine members of fronts 7 and 27 of the FARC and capture four. Offensive continues. Let's not drop our guard," Juan Manuel Santos said on Twitter.

The military is fighting the FARC despite peace talks under way between the armed group and the government in Cuba in the most promising attempt yet to bring an end to 50 years of war which have claimed more than 220,000 lives.

The government has rejected the FARC's repeated demands for a bilateral ceasefire while the talks take place, saying the best way to advance in negotiations is to maintain military pressure on the group whose membership has roughly halved over a decade.

Without a ceasefire, the FARC and its smaller National Liberation Army (ELN) counterpart, continue in turn to attack government troops and oil pipelines which carry the Andean country's most valuable export to the coast for shipment.

The peace talks have achieved agreement on about half of the agenda, with deals on land reform, political participation and ending the drugs trade which the FARC uses to fund itself.

Victim reparations and disarmament to end the conflict are two tough issues that remain to be thrashed out.