"We have received preliminary information about the killings of nine of our soldiers" in El Carmen in the North Santander department, the army said in a statement, attributing the attack to the National Liberation Army (ELN).

President Gustavo Petro on Twitter expressed his "total repudiation" of the attack.

He made no reference to the ELN, but said the perpetrators were people "still absolutely far from peace."

According to the North Santander regional government, eight other soldiers were injured.

The ELN has been in talks with the government since last November to bring an end to its near-six decade armed uprising.