The FARC guerrilla group warned Tuesday that army attacks have resulted in 20 deaths since a unilateral rebel ceasefire went into effect last month, putting peace talks in jeopardy.

The Revolutionary Armed Forces of Colombia, or FARC, accused "war-mongering sectors" of seeking to sabotage the one-sided truce, and said the attacks were making the rebels' decision to halt offensive operations increasingly unsustainable.

President Juan Manuel Santos has acknowledged that the FARC has held to the unilateral ceasefire it announced December 20, but he has refused to reciprocate.

"The deployment of troops accompanied by bombardments, landings and assaults has to date resulted in six guerrillas dead, six wounded, two captured, and the also regrettable toll of 14 soldiers dead, and five wounded," the FARC said in a statement emailed to AFP.

"Even as we alert our guerrilla forces in the country of the serious situation, we send out an SOS to the social and popular movements in Colombia," it said.

The FARC has been in peace talks with the government since November 2012 in the latest and most promising bid to end the 50-year-old conflict, Latin America's oldest.

Referring to the government's military operations, the FARC said, "Such irresponsibility has created a tense atmosphere, making the unilateral ceasefire increasingly unsustainable."

While Santos has argued that a bilateral ceasefire would allow the rebels to gain strength, the FARC said "what we see is that it is the army who is using the unilateral cessation of our offensive operations to gain a military advantage."