The explosion was so powerful that it punched several fist-size holes in a nearby concrete wall along a main highway in the suburb of Makati city, Mayor Junjun Binay said. It also ripped a large hole in the side of the bus and shattered the window abov

A powerful explosion apparently caused by a homemade bomb ripped through a passenger bus in the Philippine capital’s financial district on Tuesday, killing at least four people and wounding more than a dozen.

The explosion was so powerful that it punched several fist-size holes in a nearby concrete wall along a main highway in the suburb of Makati city, Mayor Junjun Binay said. It also ripped a large hole in the side of the bus and shattered the window above.

President Benigno Aquino III said the government had received intelligence last year that terrorist groups were plotting bombings, but at the time none of the groups appeared to have the resources to carry out the plans.

He said he directed his national security adviser to reassess those threats, but he declined to any name suspects.

In February 2005, the al-Qaeda-linked Abu Sayyaf group set off a bomb on a bus also in Makati, killing four passengers.

Mr. Aquino promised that his government would “not stop until everyone involved in this heinous crime is accounted for.”

“We will not allow this situation where there is fear among the people to continue,” he said.

The bombing appeared to have been caused by an explosive device, Mr. Aquino said, although he added that investigators had to complete their work.

Earlier, however, Metro Manila police chief Nicanor Bartolome earlier left no room for doubt about what caused the explosion- He said an improvised explosive device was placed under a passenger seat somewhere in the middle of the bus.

Fragments of what appear to be a mortar round and cell phone parts were recovered at the scene, two officials, who requested anonymity because of the nature their work, told The Associated Press.

The bus was approaching a commuter railway station when the blast occurred inside the vehicle, punching holes in windows and immediately killing a female passenger, said Binay, the area’s mayor. Three men were also killed, according to police. It wasn’t immediately clear how many people were on the bus, but some were unharmed.

Bus driver Maximo Peligro told reporters he continued driving for several more yards (meters) before stopping. Panicked passengers crowded the exit door, prompting him to kick out part of the windshield so people could jump from the vehicle that way.

The driver said he smelled gunpowder and the explosion was so loud his hearing was impaired for about 30 minutes.

Mr. Binay, who was one of the first at the scene, described a particularly gruesome sight.

“There were bones and flesh on the pavement. A bloodied body was still there. This is an act of terrorism,” he said.

Interior Secretary Jesse Robredo, who oversees the national police, said the government will hunt down those responsible.

“It’s so senseless and so ruthless that (they) will do this to totally defenseless civilians, ordinary people,” he said after inspecting the bus.

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