Two Colombian soldiers have died after an attack by fighters believed to be aligned with the National Liberation Army (ELN) rebel group. The troops were escorting a bus in the region of Arauca, on the border with Venezuela, when they were attacked by ELN fighters, local news website El Tiempo reported. Two soldiers died and three were injured in the attack, which the military blamed on the "Domingo Lain" division of the ELN.

In response, Colombian President Juan Manuel Santos said on Twitter that he had urged the country's military and police to intensify their efforts against the group.

Colombian authorities began negotiations with the ELN in Quito on February 7, as the government tries to forge a peace agreement with the group similar to that reached with the Revolutionary Armed Forces of Colombia (FARC) in November. That agreement ended a drawn-out conflict that claimed more than 220,000 lives and displaced millions over more than half a century in the country. Under the FARC peace deal, rebels were called on to move to 26 newly created transition zones ahead of handing in their weapons. The last 300 fighters reached one of the transition zones last month. The ELN group is believed to have between 1,500 and 2,000 fighters.

The attack is the latest blow to President Juan Manuel Santos's efforts to make peace with the ELN, the last active rebel group in a 53-year-old civil war that has killed more than 260,000 people and left 60,000 missing. The government, which is currently implementing a historic peace deal with rival guerrilla group FARC, opened formal talks with the ELN in February, but hostilities continue on the ground.