At least 10 guerrilla rebels from the National Liberation Army (ELN) were killed when the Colombian army bombed one of their camps in the department of Antioquia, local media reported Tuesday.

The attack resulted in the deaths of 10 guerilla fighters, including Cachaco, the leader of the ELN in Antioquia’s lower Cauca region. Three more ELN members were wounded during the operation, according to authorities, and were receiving medical attention and are currently under state custody.

The Ministry of Defense said the ELN camp was responsible for the displacement of hundreds of people in the lower Cauca region, and for attacks against electric towers in Cordoba.

The military operation took place in the early morning of Tuesday, after they were able to locate Cachaco thanks to confidential information followed up by Colombian intelligence.

The bombing occurred three days before the ELN’s unilateral ceasefire was set to come into effect. The ceasefire, announced in February, was scheduled to last between March 9 and 13 to “respect those who vote,” in Colombia’s March 11 legislative elections.

Colombia’s President Juan Manuel Santos had welcomed the unilateral ceasefire calling it the “kind of gesture we were asking from them in order to resume the dialogues” in Quito, Ecuador.

The peace talks in Quito were called off by Santos after the ELN allegedly attacked a pipeline a day after the last ceasefire ended on Jan. 9.

This latest attack by the Colombian army generates uncertainty over whether the ceasefire will be maintained and over the possibility of resuming peace talks.

This is the army’s greatest blow to the ELN since peace negotiations were called off. In late February the army accused the ELN of being responsible for the murder of five Colombian soldiers due to an explosive device that left more than 10 injured in the Santander department.