(Adds more details)

MANILA, March 18 (Reuters) - Fifteen people were injured, two seriously, in a blast outside a college near the presidential palace in Manila on Tuesday, Philippine police said.

The city's police chief said they were investigating whether a feud between college fraternities was behind the explosion, which occurred around 300 metres from the palace gates. President Gloria Macapagal Arroyo was not in the palace.

"It looks like it's ... a rivalry among a group of students," said Geary Barias, adding that part of a hand grenade and an improvised explosive device were discovered at the La Consolacion College.

The blast occurred at around 4:30 p.m. (0830 GMT) while classes were in session at the Catholic institution.

Barias said a man in a red shirt and a brown baseball cap was seen running away from the explosion. Three students have been taken in for questioning.

U.S.-style fraternities are popular in colleges and universities in the Philippines and there have been several cases of students dying during violent initiation rites. (Reporting by Michaela Cabrera and Rosemarie Francisco; Editing by Carmel Crimmins and Sanjeev Miglani)

AlertNet news is provided by