The reason is said to be violence on Thursday that led to around 30 people's deaths in Catatumbo near the border to the neighboring country Venezuela. There, battles have been ongoing for several years over cocaine trafficking between rival groups.
"What ELN did in the Catatumbo region is a war crime. That's why we're breaking off talks with this group, since ELN doesn't show any willingness to create peace" writes Colombia's President Gustavo Petro in a post on X.
ELN is the largest of the armed groups still active in Colombia since the government signed an agreement with the much larger Marxist rebel group Farc in 2016.
Last year, the peace talks were interrupted for two months after a deadly ELN attack on a military base.