MANILA - One person was killed and ten others injured when a bomb exploded Tuesday in the southern Philippine city of Cotabato, a military spokesman said.

A motorcycle packed with a homemade bomb exploded at CWAT gun store along Parang road around 2:10 pm local time.

According to Lt Col Prudencio Asto, spokesman of the Army's 6th Infantry Division, the bomb is made up of four 81 mm mortars and one cell phone that served as the triggering device.

The use of mortar rounds in the manufacture of improvised bombs is a known signature of the secessionist Moro Islamic Liberation Front, which is negotiating a peace accord with the Philippine government.

But Asto said the military has no evidence yet as to who was behind the bombing.

The bombing occurred during the second day of the Islamic fasting month of Ramadan - a holy festival among Filipino Muslims in the south. But Lt. Gen. Arthur Tabaquero, commander of the Armed Forces' Eastern Mindanao Command, said the explosion was an "isolated incident" and isn't likely to affect the month-long observance of the Ramadan.