Officials said a car bomb detonated near the state-owned oil company Ecopetrol, causing major damage to water and utility installations, Colombia Reports reported.
Soon after, unknown attackers threw two grenades at the army's Fourth Brigade headquarter as soldiers going to investigate the explosion.
There were no reports of casualties.
The attacks were blamed on the Daniel Aldana Front, a unit of the terrorist Revolutionary Armed Forces' western bloc, Colombia Reports said.
Defense Minister Juan Carlos Pinzon condemned the attacks, Tuesday saying they were "indiscriminate attacks of terrorism with the intention of harming the civilian population."
Colombia Reports said Tumaco is a transport hub for cocaine traffickers because of its location near the Pacific coast and its proximity to some of Colombia's most extensive coca growing areas.