Marxist rebels in Colombia have ambushed a military convoy, killing 17 soldiers, the army chief has said.
The Farc is believed to be behind a number of recent attacks on troops
The patrol came under attack in the violent oil-rich state of Arauca on the border with Venezuela, which rebels use for drugs and weapons smuggling.
Some wounded soldiers were finished off with shots to the head, said Gen Reinaldo Castellanos.
It is another blow to government claims that Revolutionary Armed Forces (Farc) rebels are retreating, say analysts.
In the latest attack, explosives were detonated as the patrol was passing between Fortul and Tame, some 40km (240 miles) north-east of the capital Bogota.
An army major and three other officers were among those killed, said Gen Castellanos in a statement.
He said he was travelling to the area on Thursday to support his troops.
The Farc has carried out a series of attacks against the Colombian military in recent months.
Eight soldiers and one civilian were killed when mines detonated on a bridge in Putumayo province as their patrol crossed on 3 February.
Two days earlier, rebels attacked a military outpost in the village of Iscuande with home-made rockets, killing at least 14 marines and wounded more than 20 others.
Colombia's President Alvaro Uribe launched a major security crackdown upon coming to office more than two years ago.