Colombia's military says 57 soldiers have been kidnapped by civilians in the country's south-western Micay Canyon area.
It says 31 soldiers were seized on Saturday while the rest were abducted on Sunday by a group of more than 200 people.
The military says the civilians are acting under pressure from dissidents of the Farc rebel group which agreed a peace deal with the government in 2016.
The mountainous region is a key zone for cocaine production and remains one of the most tense in the country's ongoing conflict with rebel groups.
In a video statement on social media, Brig Gen Federico Alberto Mejia said four non-commissioned officers and 53 soldiers had been seized over the weekend.
"This is called kidnapping," he said.
Reports in local media suggest that the EMC rebel group - the largest offshoot of the Farc - may have ordered the kidnappings.
The EMC has not commented on the issue.
The Micay Canyon is used for transporting cocaine to Pacific ports, and drugs are then illegally shipped to other countries.