The insurgents attacked soldiers guarding a pipeline in the Norte de Santander district which borders Venezuela.
A military Black Hawk helicopter flying over the region to protect oil infrastructure also exploded after triggering a mine while landing, officials said.
Meanwhile, another attack by the Revolutionary Armed Forces of Colombia (FARC) on an oil pipeline late Sunday caused a spill in the Narino department in the southwest.
This is the second time in a week the Marxist group has reportedly attacked government forces and a pipeline, continuing a series of attacks since FARC suspended a unilateral ceasefire in May.
Last week, rebels sabotaged the country's Cano Limon-Covenas pipeline, its second largest, in the north of the country and then attacked an army patrol in the south, killing four soldiers and wounding four others.
The escalating attacks against infrastructure and government forces come as talks in Cuba to end the country's 51-year-old conflict show signs of fraying.
Although the talks have advanced on a number of major issues, a final accord has yet to surface.
In April, President Juan Manuel Santos resumed airstrikes against FARC after the killing of several soldiers in a guerilla ambush.
More than 200,000 people have been killed in Colombia's conflict since FARC was launched in 1964.