Zamboanga City, Philippines - A homemade bomb was found Thursday near a government building in a southern Philippine city amid tight security on the anniversary of the September 11, 2001, terrorist attacks in the United States, police said.

The explosive device, made with 3 kilograms of ammonium nitrate, was concealed in a black plastic bag left in a vacant lot in front of the local legislative building in Zamboanga City, 875 kilometres south of Manila.

The bomb was defused by police officers, said Superintendent Jose Bayani Gucela, chief of the police's regional explosive ordnance and disposal unit.

He said a teenager found the bomb before dawn and immediately reported it to police.

Gucela said authorities had yet to identify a suspect in the attempted bombing.

Police forces nationwide were on heightened alert against terrorist activities by local groups on the seventh anniversary of the suicide hijackings that targeted New York and Washington.

Chief Superintendent Nicanor Bartolome, national police spokesman, said forces were ordered to "intensify intelligence operations to monitor and pre-empt movement of known threat groups and strengthen the defenses of vital installations and soft targets."

The al-Qaeda terrorist network, blamed for the September 11 attacks, is believed to be providing financial support to the local Muslim Abu Sayyaf rebel group and the regional terrorist network Jemaah Islamiyah, whose top militants are hiding in the southern Philippines. (dpa)