The Colombian government suspended talks with leftist rebels on Monday in response to the group's kidnapping of a top Army general, a major setback for the two-year-old peace process.

Armed men captured Gen. Rubén Darío Alzate and two others while they were surveying a rural energy project in western Colombia on Sunday, the Associated Press reports. The kidnapping by the Revolutionary Armed Forces of Colombia, or FARC, threatens ongoing efforts to end 50 years of war. With no immediate reaction from the rebel group, its motives remain unclear.

Colombian President Juan Manuel Santos said the peace talks currently under way in Cuba would be suspended until Alzate and the two others – an Army captain and a female civilian lawyer – are released. He called off plans for his negotiation team to fly to Havana on Monday.

"This kidnapping is completely unacceptable," Mr. Santos told reporters late Sunday night, according to media reports. "The FARC is responsible for the life and the security of these three people."

The president said troops would be sent to the area to attempt to rescue the three captives, who were captured after disembarking from a boat on a river near the city of Quibdo. A soldier who escaped in the boat said the kidnappers belonged to the FARC's 34th front, one of its most entrenched divisions, the AP reports.

The incident is the first time in a half-century of fighting that the FARC have captured such a high-ranking Army general, according to Colombia Reports, an independent English-language news website. It called the kidnapping a "major blow" for Santos.

The suspension appears to be a breach of the warring parties' initial promise to not let acts of war influence the continuation of talks as a ceasefire between the warring parties was not agreed for the duration of the talks.

The president has rejected the FARC's continued demands for a cease-fire, fearing that establishing one would allow the guerrillas to regroup, AP reports.

The Wall Street Journal called the decision to suspend the peace talks, launched two years ago in an effort to end the simmering conflict, a "bold step."

[Santos] has made achieving peace with the FARC the cornerstone of his presidency. He was re-elected to a second, four-year-term in June on the promise of inking a final accord. The president has pledged that peace will bring greater economic expansion and foreign investment to Colombia. But the capture of a general has angered officials here, who see it as a signal that the FARC isn't negotiating in good faith, people close to the matter said Sunday.

Santos publicly warned the FARC that they risked jeopardizing the peace process after they abducted two soldiers last week and continued attacks on infrastructure, Reuters reports. The rebel group swore of kidnapping in 2012 but maintains that military personnel are fair targets in the absence of a cease-fire. It called the detained soldiers prisoners of war.

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The suspension announced Sunday is not the first time the peace talks have been derailed. The FARC stopped them in August 2013 amid suspicions surrounding the government's plan to put any peace deal to a referendum. They were resumed at the end of the month, The Christian Science Monitor's Sibylla Brodzinsky reported.

An estimated 220,000 people have died in Colombia since the armed conflict began in 1964, the BBC reports.