Police investigators check on the damage of a passenger bus after an explosion Tuesday in Manila. (AP)MANILA: A bomb on a packed bus in the Philippines' financial hub killed four people Tuesday, sparking a warning from President Benigno Aquino that the country faced a raised terror threat. Authorities said it was too early to say who was behind the explosion as the bus traveled along one of Manila's busiest roads, but Aquino ordered security forces on alert. “We have asked the police and military and the intelligence services to review their threat assessment, with the end view of hardening all areas considered under threat,” Aquino said. “So far the investigation is ongoing, but the mechanical and electrical causes are being ruled out for this explosion. There appears to be an explosive device... we are looking at the terrorist aspect of it.” Metropolitan Manila police chief Director Nicanor Bartolome said the bomb appeared to have been placed under one of the passenger seats. Vice President Jejomar Binay, a former mayor of the Makati financial district, arrived quickly at the scene and said it appeared to be a powerful blast. “There's a huge hole and the debris indicates it is a bomb,” Binay said, adding the legs of one injured woman had been blown off. Investigators were seen scouring the scene for evidence, with blood drying on the pavement. The driver, who survived the attack unscathed, said at least two men who acted strangely quickly got off the bus just moments before the explosion. The Philippines faces a range of security threats, most prominently the Abu Sayyaf militant group that operates mainly in the south of the country, and communist rebels who have been waging a rebellion for 42 years.
