The soldiers were surrounded by "nearly 200 people and forcibly transferred, against their will, to an indigenous reservation" in Choco Department in the country's northwest, near the border with Panama, Sanchez said in a post on X.

Founded in 1964 and inspired by the Cuban revolution, the ELN, or National Liberation Army, is the oldest surviving guerrilla group in the Americas.

The group controls key drug-producing regions of Colombia, which is grappling with its worst security crisis in a decade, fueled by criminal groups profiting from trafficking, extortion and illegal mining.

The defense minister condemned the kidnapping of the troops, saying that restricting military operation puts local communities at "serious risk."

"These operations aim to protect the civilian population -- especially indigenous communities -- from threats such as the recruitment of minors, forced displacement, and other acts associated with violence," Sanchez said.

"Peace is not built by kidnapping soldiers or weakening the state," he added.

Sanchez said he had asked the the interior ministry, the Choco government and human rights organizations to help secure the safe return of the soldiers.

A criminal complaint has also been filed with the attorney general's office.

Choco Governor Nubia Cordoba said that after "the detention of 18 soldiers who were carrying out their legal duties," she called an "extraordinary security council" to seek their release.

In September, 72 soldiers were detained by hundreds of residents in the Micay Canyon, an enclave for cocaine production dominated by dissident rebels from the now-defunct FARC group.

A month earlier, 33 uniformed personnel were freed after being held for three days in the department of Guaviare.