Three Colombian soldiers were killed when an explosive device blew up the armored vehicle they were sitting in on Feb. 15.

The Colombian army stated the device was planted by Colombia's second largest rebel group, the National Liberation Army (or, ELN).

According to BBC, the deadly attack occurred in the Norte de Santander province, an area close to the border with Venezuela where the the Marxist group has a fortified base.

In 2014 the ELN made announcements it was willing to commence peace talks with the Colombian government. But, despite the supposed attempts to resolve differences, formal talks between the two sides have yet to begin.

The ELN, a rebel group that advocates a composite Communist ideology of Marxism and Liberation Theology, was founded in 1964 in order to fight against what they saw as Colombia's unequal distribution of land and riches

Classified as a terrorist group by the U.S. State Department Foreign Terrorist Organizations in 1997, at present the ELN is estimated to have some 1,500 active fighters within its circle.

Although the group is smaller and has power over less territory than Colombia's No. 1 Marxist rebel group, the Revolutionary Armed Forces of Colombia, they have been responsible for consistent acts of aggression over the years.

As detailed in a Stanford report, in the 1980s most of the group's funds came from kidnapping and extortion.

In 1999 its guerrillas hijacked an Avianca flight, landed the plane in a remote location and took all the passengers and crew as hostages.

In 2011 the ELN fought with the Colombian army in the Norte de Santander province along the Venezuelan border, and in the process three people were killed, and four were injured.

Peace talks between the larger rebel group, the Revolutionary Armed Forces of Colombia, and the government have been going on for more than two years. The latest discussion took place just last Thursday.