Fighting between rival rebel groups in the border region between Colombia and Venezuela left at least 23 people dead, officials reported on Monday.

The clashes were believed to have been between militants from the National Liberation Army (ELN) and remnants of the Revolutionary Armed Forces of Colombia (FARC) who refused to lay down arms in the 2016 peace deal.

Colombian President Ivan Duque said that civilians who had been caught up in the fighting were "likely" among the deceased.

Duque blames Venezuela

"I've mobilized two battalions to support the task of getting the regions under control in the next 72 hours," Duque said.

Violence was reported in the areas of Tame, Fortul, Saravena and Arauquita.

"These groups [the ELN and FARC] have been operating at ease in Venezuelan territory with the consent and protection of the dictatorial regime," the president added.

Colombia frequently accuses its neighbor of harboring rebel forces. The two countries ended diplomatic ties shortly after Duque became president.

Civilians caught up in violence

One Colombian official said that a dozen families had to flee the fighting, while local authorities reported that others were trapped in the crossfire.

Jose Miguel Vivanco, the Americas director for Human Rights Watch, called the situation on the border "very serious."

Violence in the country has increased despite the deal signed between the former Colombian president Juan Manuel Santos and the FARC that saw 13,000 rebels lay down their arms.

There are thought to be some 5,000 remaining FARC guerrillas as well as 2,500 active ELN members.

Various groups, including paramilitaries and drug gangs, are also fighting over the gains from drug trafficking and illegal mining.

ab/fb (EFE, AFP)