Soldier aids a comrade wounded during a rebel attack toward a helicopter at a military base in Vista Hermosa

Rebel forces in Colombia killed 28 soldiers Tuesday in the deadliest assault on government troops in years.

The attack happened near the town of Vista Hermosa, south of the capital city of Bogota, near an area controlled by the Revolutionary Armed Forces of Colombia, or FARC. Military officials say the soldiers were guarding workers as they destroyed crops of coca, the plant used to make cocaine.

The 17,000 strong FARC, along with a smaller guerilla group known as the ELN, has been engaged in a deadly 40-year civil war to topple the government. It funds its operations mainly through drug trafficking.

Colombian President Alvaro Uribe, who is running for re-election in next May's presidential vote, has stepped up military efforts against FARC forces in the region.