Seventeen soldiers were killed and four injured when guerrillas attacked their patrol in northeast Colombia, the army said in a statement Friday.

The attack by the Gabriel Galvis unit of the Revolutionary Armed Forces of Colombia took place around 11 p.m. local time Thursday near the town of Abrego, 190 miles northeast of Bogota.

Luis Miguel Moreli, governor of Norte de Santander state where the attack took place, said the army and rebels were locked in heavy combat in the area.

"The truth is we've suffered some important casualties," he told Caracol Radio. "In this area there's always the chance of a tragedy occurring."

The FARC has been flexing its military muscle of late in defiance of President Alvaro Uribe's order to intensify the military campaign against the insurgents.

Click here to go to FOXNews.com's Americas Center.

Last month, 17 police officers were killed when some 400 rebels bombarded a police station with makeshift mortars than attacked a column of reinforcements in a remote hamlet in the country's northwest.

After a bombing at a Bogota military base in October that injured 23 people, Uribe halted peace overtures with the FARC, Latin America's oldest and most potent insurgency.

Gen. Mario Montoya, commander of the army, had traveled to Norte de Santander state — one of Colombia's deadliest areas, long disputed by rebels and right-wing paramilitary groups — to coordinate a counteroffensive against the rebels.

The FARC has been trying to overthrow Colombia's government for almost a half-century. After being pursued the past four years by Uribe's U.S.-trained military, its numbers are believed to have thinned to about 11,000 fighters.