Manila: Fifteen people were injured, two seriously, by a blast outside the presidential palace in Manila, Philippine police said on Tuesday.

The blast occurred around 4:30 p.m local time in front of the La Consolacion College at Laurel Street near the sentry gate of the Presidential Security Group, Philippine TV network ABS-CBN reported.

Manila's police chief Geary Barias said they were investigating whether the blast, which occurred about 300 metres from the palace gates, was caused by a grenade.

"A safety lever of a hand grenade was found," said Barias.

The victims were brought to the Manila Doctors Hospital and University of Sto. Tomas Medical Center.

Bomb experts were called in and authorities are investigating the incident.