Colombian rebel group the National Liberation Army (ELN) is holding two soldiers hostage after capturing them in an attack that killed 12 troops and police, officials said.

"Two soldiers have been kidnapped," said Defense Minister Luis Carlos Villegas after President Juan Manuel Santos convened an extraordinary meeting of his national security council in the wake of Monday's attack in the remote indigenous reserve of Bachira.

The attack, which the government said killed 11 soldiers and one police officer, targeted a convoy transporting result sheets from the country's local and regional elections Sunday.

It disrupted what Santos had called the most peaceful elections in conflict-torn Colombia's recent history.

The ELN, the smaller of two leftist guerrilla groups fighting the Colombian government since the 1960s, has staged a series of recent attacks, even as the government closes in on a peace deal with rival rebel group the Revolutionary Armed Forces of Colombia (FARC).

Monday's attack also left three soldiers wounded. A policeman and a guide from the indigenous U'wa group are still missing.

Villegas said the government holds the ELN responsible for the "life and safety" of the two soldiers and reiterated the president's vow to continue the army's offensive against the group.

The ELN took credit for the attack but disputed the toll, claiming on Twitter it had left "17 army troops and a police officer dead plus several injured."

It said the two army hostages, which it named as Andres Felipe Perez and Klieder Antonio Rodriguez, "are in perfect health."

Meanwhile, the army said it had captured three rebels suspected of taking part in the attack in an anti-ELN operation in the same area.

"Three captured, including one wounded," General Alberto Mejia wrote on Twitter.

The government estimates the ELN has some 2,500 fighters and the FARC around 7,000.

The ELN and the government have been holding preliminary talks since January 2014, but have not opened a formal peace process.

The nearly three-year-old peace talks with FARC rebels have made progress on key issues in recent weeks, and Santos has vowed to reach a deal by the end of March.

The Colombian conflict has killed more than 200,000 people and uprooted six million since it erupted in 1964.
Source: AFP