Leftist rebels killed at least five oil contractors for Colombian state-controlled energy firm Ecopetrol in an explosives attack on an oil well.

"Five workers from the Independence and Contransur firms were killed" and three others were injured Wednesday while fixing the Sibundoy 1 well outside the southwestern town of Puerto Caicedo, Putumayo province, Ecopetrol said in a statement.

The injured were taken to a hospital in the city of Puerto Asis, while the other workers were unharmed.

The commander of the Colombian army's 27th Jungle Brigade, Gen. Jose Guillermo Delvasto, told reporters that Revolutionary Armed Forces of Colombia, or FARC, guerrillas carried out the attack.

Troops from the 25th Infantry Battalion were deployed to the area to track down the perpetrators.

"The companies are providing the security forces with all information and cooperation necessary to clear up what happened and reinforce the security measures that safeguard workers' lives and their operations," Ecopetrol said.

The state oil firm has installed significant infrastructure in Putumayo and also operates the 306-kilometer (190-mile) Transandino pipeline, which links Ecuador's border region to the Colombian Pacific port of Tumaco. EFE