MANILA : Military explosives were used in a huge bomb blast at a Manila shopping mall that left nine dead and 113 injured, Philippine police said Saturday.

Evidence collected from Friday's Glorietta mall blast indicates that the bomb "contained RDX, the main chemical component of C4," the police said in a report to Philippines President Gloria Arroyo.

In the Philippines C4 explosive is only used by the military.

The report was delivered at a top-level security meeting between the president and her security advisers at police headquarters in Manila.

Arroyo immediately ordered the country's police chief General Avelino Razon to check its source and pin-point the culprits.

"Is that already definitive... or is there going to be another more detailed finding of what kind of explosive was used?" Arroyo said during the briefing. "We need regular information bulletins on the status of the investigation."

Senior Superintendent Bert Ferro, who heads the police bomb data centre, said samples taken from the site leads him to "presume that those are of military ordnance components."

A chemist from the centre told Arroyo that it was possible that more samples were being collected from the site, but "at this point in time, that is what we have."

Razon said the government was putting up a two-million-peso (45,454-dollar) reward for any information leading to arrests.

No group has claimed responsibility for the blast, which came weeks after military intelligence foiled an alleged plot by Al Qaeda-linked Abu Sayyaf Islamic militants to bomb the southern port city of Zamboanga.

National Security Adviser Norberto Gonzales said authorities were also looking at the Abu Sayyaf as possible suspects, noting that the group may have carried it out as part of their campaign to attract funding from international terrorist groups.

Reports said officials from the US Federal Bureau of Investigation (FBI) were helping Philippine police in the probe.

Throughout the night bomb experts sifted through blast debris trying to find clues as to what sort of bomb was used.

The mall remained sealed Saturday, with a cordon of policemen guarding its perimeter.

Razon said the bomb was apparently left at a delivery bay near a popular Chinese restaurant at the mall shortly after lunch.

He said investigators were also reviewing closed circuit television cameras and interviewing survivors and witnesses.

Security in all malls, bus and train stations, as well as sea and airports have been intensified, Razon said, with elite police commandos patrolling streets.

Alfie Reyes, a spokesman for the mall owners Ayala Land, said the firm would pay all medical expenses for the victims.

Officials and witnesses said the explosion left an eight-metre-wide (26 foot) crater on the ground floor and blew a hole through the roof on the second floor.

Abu Sayyaf Islamic militants were blamed for the bombing of a bus near the Glorietta mall that killed four people on Valentine's Day in February 2005.

Militants also firebombed a ferry in Manila Bay the previous year, killing more than 100 people in the country's worst terrorist attack.

- AFP/so