At least eight people were killed in an attack on a civilian bus by left-wing rebels Farc in southern Colombia.
The Farc is flexing its muscles ahead of the May poll
Rebels shot at the bus tyres, causing it to crash, and then opened fire on passengers and attempted to set the vehicle ablaze, the military said.
The bus was travelling in a convoy under army escort but had fallen behind as it stopped to pick up passengers.
The Farc has tried to impose a ban on the movement of all vehicles in Caqueta province for the last 10 days.
The attack occurred on a remote highway near Puerto Rico, 310km (190 miles) south-west of the capital Bogota.
The Farc said the traffic ban was aimed in part in protest at the re-election bid of hard-liner President Alvaro Uribe.
Mr Uribe, who has vowed to wipe out the Farc through military force, is likely to be returned to office come May's election.
Several vehicles which ignored the ban have been fired upon and set alight prompting the army to introduce armed escorts.
The Farc (Revolutionary Armed Forces of Colombia) has been fighting the government for more than four decades.