Anti-government protesters caused a pipeline explosion in southern Bolivia yesterday, forcing a 10-per-cent cut in natural gas exports to Brazil, the head of the state energy company said. The official, Santos Ramirez, called the explosion in Tarija province ''a terrorist attack.'' The company said protesters closed a valve, which created pressure that ruptured the pipeline and triggered a fire near the border with Paraguay. There were no immediate reports of injuries. President Evo Morales' leftist government immediately ordered additional troops dispatched to Bolivia's rebellious eastern provinces to secure gas and oil installations seized by demonstrators in protests that have become increasingly violent. ...