Colombian authorities discovered a drone carrying explosives near Bogota’s airport and a nearby military base, raising security concerns in the capital, a senior army source said Friday.

Authorities found the fiber optic drone on Wednesday, around 5.4 kilometers (3 miles) from the air base, which abuts El Dorado International Airport, the source told AFP.

The find comes amid a wave of attacks by drug-trafficking left-wing guerrillas in the run-up to the May 31 presidential election.

The military said the drone was believed to belong to one of the guerrilla factions.

Several of the Colombian armed groups that remain at war with the state have stepped up their use of drones in attacks on military bases and police stations.

Fiber-optic drones, which are resistant to jamming, have become a feature of the conflict between Russia and Ukraine.

The Colombian army official, who was not authorized to speak on the record, said the tip-off about the drone came from the prosecutor's office of the restive southwestern Cauca department.

A bomb attack on a busy road in Cauca killed 21 people on April 25 – the deadliest attack involving civilians since the defunct FARC rebel army blew up a Bogota nightclub in 2003.

Dissident FARC rebels opposed to a landmark 2016 peace deal claimed responsibility for the Cauca attack and said they had not meant to target civilians.