Presumed leftist rebels attacked a small police convoy in Colombia's turbulent northeast on Friday with explosives and automatic weapons, killing eight police officers and wounding one.

The slain officers, traveling in a four-wheeled vehicle and on two motorcycles, were responding to an anonymous tip about a cadaver supposedly found near a cemetery not far from their base in Fortul, the Arauca Province police chief, Col. Luis Ortiz, told The Associated Press. He said it appeared the bomb blast was triggered by remote control.

The rebels finished off the police with gunfire, said Colombian Defense Minister Juan Manuel Santos, who blamed the attack on leftist rebels.

The Revolutionary Armed Forces of Colombia, or FARC, and the much smaller National Liberation Army, or ELN, both operate in the oil-producing region bordering Venezuela.

While Colombia has seriously debilitated the rebels in the past two years, thanks in great measure to U.S. military assistance, they remain capable of damaging hit-and-run attacks.

In the first 10 months of this year, 331 police and soldiers were killed in combat, down from 467 in the same period last year, according to the Defense Ministry.

Santos says the FARC has been reduced to fewer than 8,000 fighters, less than half its strength when law-and-order President Alvaro Uribe first took office in 2002.

Those gains were marred recently by a scandal over hundreds of killings of civilians that prompted a high-level purge of the army last month.