At least eight people were killed in the Philippine capital, Manila, when an explosion rocked the Glorietta shopping mall in the financial district of Makati.

Police still aren't sure whether the blast was caused by a bomb, Manila Police Chief Geary Barias told reporters at the site. As many as 70 people have been hospitalized, he said.

Philippines National Police Chief Avelino Razon said in an interview on DZBB radio earlier that the extent and destruction of the blast suggested it had been caused by a bomb.

Manila police are on full alert, Barias said. President Gloria Arroyo ordered officers to ''get to the bottom'' of the incident.

If the explosion is confirmed as a bombing, it would be the first in Manila since a bus blast killed six people in February 2005. Abu Sayyaf, a terrorist splinter of the country's Muslim separatist movement, claimed responsibility for that attack.

ABS-CBN television broadcast images of the mall, owned by Ayala Land Inc., showing extensive damage, including part of its elevated walkway collapsed on cars.

''There was a loud explosion and people started running,'' said Antonio San Juan, a cook at a restaurant at the mall. ''There was smoke and dust everywhere.''