At least 22 people were injured when an improvised bomb exploded at a plaza in the southern Philippine city of General Santos Wednesday night, a military spokesman said on Thursday.

"(There's) no suspect yet since investigation is still being conducted," said Romeo Brawner, a spokesman for the Philippine Army.

The blast took place at 9:30 p.m. local time (1330 GMT) on the New Year's Eve.

The victims are now in different hospitals for prompt medical treatment, Brawner said.

On Thursday morning, authorities discovered another powerful improvised explosive device left near a passenger bus terminal in Zamboanga, another city in the restive south.

The explosive was assembled from an 81-millimeter mortar bomb and connected to a clock, Philippine TV network GMA News reported.

Since last week, government troops and police forces have been placed on alert in the south as Filipinos celebrate the Christmas and the New Year. The Moro Islamic Liberation Front, the country's largest rebel group with 12,000 members, are at war with the government troops for the establishment of a separate Islamic state.

Earlier this week, an improvised bomb loaded on a tricycle exploded near a check-point in southern Philippine province of Sultan Kudarat, killing the tricycle driver while wounding a policeman.

(Xinhua News Agency January 1, 2009)