The second-biggest oil pipeline in Colombia has been temporarily closed following three bomb attacks, state energy company Ecopetrol said Monday, and security forces blamed the explosions on leftist guerrillas. The closure of the 780-kilometer Cano Limon-Covenas pipeline owned by Ecopetrol did not immediately affect exports or oil production by U.S. producer Occidental Petroleum, which feeds oil into the pipeline from a field it operates near the Venezuelan border. Militant groups have attacked oil infrastructure with increasing frequency over the last year, even with peace talks being held between the government and Revolutionary Armed Forces of Colombia (FARC) rebels.