BOGOTA: Twelve people were wounded Wednesday when a bomb exploded outside the Colombian intelligence agency`s offices in the southern city of Pasto, near the Ecuadoran border, the Red Cross said.

A "low-intensity package bomb was left outside the Administrative Department of Security (DAS) building, next to a lamppost, by a man who then ran away," Pasto Red Cross official Henry Palacios told AFP.

He said 12 passersby and workers from the DAS building were wounded in the blast and taken to area hospitals.

Narino department Governor Antonio Navarro told Caracol radio that two of the wounded were in serious condition and that the damage wrought by the bomb was considerable.

He said authorities suspect the bombing was the work of the leftist Revolutionary Armed Forces of Colombia (FARC), the country`s oldest and strongest rebel group.

Shortly after the blast, DAS agents detained a man and a woman who were leaving the area in a taxi and are suspected of being behind the blast, DAS Director Felipe Munoz said.

Pasto is the capital of Narino department, one of the FARC`s strongholds in southern Colombia. On Tuesday, six police officers on road patrol were ambushed and killed in Samaniego.

FARC guerrillas have stepped up their attacks since President Juan Manuel Santos took office on August 7 and rebuffed the rebels` offer of peace talks, demanding instead that they lay down their weapons and release all their hostages.

BDST: 1126 HRS, SEP 09, 2010