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Colombian Army press office, Associated Press
This Aug. 15, 2014 photo released by Colombia's Army press office shows Colombian Army Gen. Ruben Dario Alzate, left, reaching to shake hands with a soldier in Bogota, Colombia. Colombian President Juan Manuel Santos suspended peace talks with the South American nation's largest rebel group after Alzate was taken captive on Sunday, Nov. 16, 2014. The U.S.-education soldier and two others were intercepted while traveling by motor boat along a remote river in western Colombia. A fourth soldier managed to flee and reported that the captors were members of the 34th front of the Revolutionary Armed Forces of Colombia, or FARC.

BOGOTA, Colombia — A massive search operation was under way Monday for a Colombian army general whose surprise capture by leftist rebels prompted President Juan Manuel Santos to suspend two-year-old peace talks.

Gen. Ruben Dario Alzate was surveying a rural energy project along the remote Atrato River in western Colombia when he and two others were snatched Sunday by armed men. A soldier who managed to flee in the group's boat said the kidnappers belonged to the 34th front of the Revolutionary Armed Forces of Colombia, or FARC.

Colombian media reported it's the first time in a half-century of fighting that the guerrillas have taken an army general captive.

Calling the abduction "totally unacceptable," Santos said he had ordered government peace negotiators not to travel Monday to Cuba for the next round of peace talks. Those talks will not resume until Alzate and the two others — an army captain and a female lawyer — are freed, he said.

"The FARC is responsible for the life and safety of these three people," Santos told journalists after midnight after meeting with his top military commanders before they left for the western city of Quibdo to oversee rescue efforts.

The surprise blow comes as frustration with the two-year-old peace talks builds over slow progress and the guerrillas' apparent refusal to wind down attacks in areas where they remain dominant. In the past few days, the FARC captured two soldiers following intense fighting in northeast Colombia — it has since offered to free them — and killed two members of an indigenous tribe who confronted rebels.

The FARC swore off kidnapping of civilians in 2012 but considers captured military personnel prisoners of war. It also has been clamoring for a cease-fire while peace talks continue, something Santos has rejected for fears it would allow the guerrillas to regroup after years of battlefield defeats at the hands of Colombia's US-backed military.

The FARC's 34th Front is among the group's most-entrenched, operating in the dense, water-logged jungles around Quibdo where a slew of criminal gangs and drug-traffickers also operate.

Santos, who was re-elected in June, has staked his presidency on reaching a deal with the FARC. But he's struggled to overcome doubts from conservative opponents and members of the military who fear he's ceding too much power to rebels behind scores of atrocities.

In a sign of growing tensions with his military, the president Sunday night demanded to know why one of Colombia's most distinguished soldiers apparently violated military protocol and set off on the river in the dangerous conflict zone dressed as a civilian and without bodyguards.

The U.S.-educated Alzate took over as commander this year of the newly established Titan Task Force, a 2,500-man counterinsurgency force operating from Quibdo.

There was no immediate reaction from the rebel group.

Follow Joshua Goodman on Twitter: @APjoshgoodman