The ELN -- or National Liberation Army -- had called on Friday for a 72-hour lockdown in areas it controlled beginning on Sunday morning, saying it would be carrying out military exercises in response to "intervention" threats from US President Donald Trump.

On Sunday, it released another statement further warning people in cities, including the capital Bogota and metropolis Medellin, to avoid military installations during the three days of what it is calling an "armed strike."

Petro, in a post on X accompanying the ELN notice, said: "These are not threats to Trump, they are threats to Colombia."

"The order given to Colombia's security forces is to attack the ELN and defend the Colombian people against any external threat," he said.

Petro urged Colombians to go out for Christmas activities without fear.

"Fear paralyzes and we will not let ourselves be threatened by foreign powers or by drug traffickers dressed as revolutionaries," Petro wrote.

Later on Sunday, the army reported it had thwarted three attempts by the ELN to carry out attacks with explosives on roads in Norte de Santander, a department on the border with Venezuela, and in southwest Cauca department.

The ELN was founded in 1964 and inspired by the Cuban revolution. Experts estimate it has a presence in at least 20 percent of Colombia's more than 1,100 municipalities.

Petro, Colombia's first leftist president and himself a former guerilla, sought to negotiate peace with the rebels after taking office in 2022, but the talks failed.

Negotiations tanked last January after the ELN killed more than 100 people in a region bordering Venezuela.

The guerrillas, who traffic cocaine, believe the US plans to carry out military operations in Colombia as part of a neocolonial plan under Trump.

Petro has similarly denounced threats from Trump of potential US military action in Colombia against drug traffickers.