Bogota: At least 18 Marxist rebel fighters were killed during an operation by Colombia's army on Thursday, in one of the most deadly confrontations since the guerrillas began peace talks with the government more than two years ago.

The bombing raid, followed by ground combat, took place in Cauca department on the Pacific coast, the army said, a key drug trafficking region where the Revolutionary Armed Forces of Colombia, or FARC, have a large presence.

The FARC began negotiations with the government of President Juan Manuel Santos to end five decades of war at the end of 2012, in a bid to halt a conflict that has killed more than 220,000 people and displaced millions.

‘A military offensive produced combat in which 18 rebels died,’ an army official told Reuters. The military did not immediately report any casualties.

The rebel deaths come a month after the FARC broke a unilateral ceasefire and killed 11 soldiers, a move that prompted the government to restart suspended bombing raids on guerrilla camps.