BOGOTA, Colombia — The leader of Colombia's once-largest guerrilla group who is now campaigning for president has been hospitalized after experiencing chest pain.

The group known as the Common Alternative Revolutionary Force said Thursday Rodrigo Londono is under medical observation.

A doctor at the San Rafael Hospital told BLU Radio he may have suffered an "acute coronary" event.

Londono is best known by his alias Timochenko and has suffered various health setbacks in recent years. He experienced a heart attack in 2015 during peace talks in Cuba and a stroke last year.

The former rebels are transitioning to civilian life after reaching an historic peace accord to end Latin America's longest-running conflict in 2016.

Timochenko's bid for president has been rife with conflict, with angry Colombians throwing eggs at him on several occasions.