The Revolutionary Armed Forces of Colombia (FARC) guerrillas blew up an oil pipeline on Thursday, leaving an estimated 16,000 people without water, according to officials.
The attack occurred near the municipality of Catatumbo, in northern Colombia.
The resulting spill has contaminated a river forcing the water supply to be cut, the local authorities said.
The FARC separatists have stepped up their attacks on infrastructure since they unilaterally suspended their ceasefire on May 22nd.
In another incident not directly related to the latest attack, four government military personnel were killed when they stepped on landmines in the southern region of Caqueta, which also injured four others.
The mines had been laid by FARC, the government said.
The left-wing group had been engaged in peace talks with government negotiators since November 2012, which looked to end more than 50 years of violence. While there has been agreement on several points and the negotiations continue to take place in the Cuban capital of Havana, attacks by the guerrillas have continued to occur since the lapse in the ceasefire.
A similar attack on an oil pipeline contaminated the Canaupi river in south-west Colombia on June 12th and the group ambushed and killed 11 soldiers in May.
President Juan Manuel Santos responded to the violence by ordering the resumption of bombing raids on rebel positions, though it remains unclear how effective such strikes have been given the dense jungle in which FARC operates.
Last week the rebels cut off power to almost half a million people in Caqueta, according to the military, by bringing down an electricity pylon.