BOGOTA, Colombia -- Suspected rebels detonated a car bomb Thursday, killing four civilians and wounding at least 15 near an area where U.S. special forces will soon train Colombian troops.
It was the second car-bomb attack in two days in northeast Colombia's Arauca state. In both cases, the drivers were in the cars when they blew up, and both died.
Army Gen. Martin Orlando Carreno said he did not know if the bombings were suicide attacks or if the drivers had been forced or tricked into taking part.
Colombian rebels have not been known to use suicide bombers.
The bomb exploded on a road near a military checkpoint at the entrance to the town of Fortul, 220 miles northeast of Bogota. In Saravena, some six miles away, U.S. Army Green Berets and other American special forces will begin training Colombian troops in counterinsurgency tactics this month.
The Colombian troops are to protect an oil pipeline that carries oil belonging to Los Angeles-based Occidental Petroleum. The pipeline has been dynamited by rebels many times.
Carreno said he believed the Revolutionary Armed Forces of Colombia, or FARC, was responsible for the attack.
Wednesday's car bomb went off in front of a military base in Arauquita, 30 miles east of Saravena, killing the driver of the car and wounding two soldiers.
Despite efforts by President Alvaro Uribe to beef up security in the area, Arauca state remains one of the most dangerous areas in Colombia.
Colombia is torn by a 38-year civil war that pits the rebels against the government and outlawed paramilitary groups. About 3,500 people, mainly civilians, die each year in the fighting.