The Colombian army says it's searching for the bodies of eight soldiers who were killed in an attack by left-wing rebels on Thursday.

Fifteen others are missing.

The army said that rebels from the Revolutionary Armed Forces of Colombia FARCtried to shoot down an army helicopter during the clash near Chameza in Casanare department in the northern Andes, but the helicopter had managed to return to base.

The Colombian army has stepped-up operations in the run-up to Sunday's presidential election.