The 40-mm grenade went off against the Notre Dame University dormitory in Busbus district, a Muslim residential area near the local Army base, Col. Alexander Aleo said.
"Witnesses said they heard a speeding vehicle followed by a blast," Alex said, indicating the perpetrators had fired the grenade from a moving vehicle, then sped away.
However, he expressed doubt that the blast was linked to a series of bombings in Zamboanga City or continuing military operations against Abu Sayyaf guerrillas in Sulu.
"It looks like a feud with no relation to terrorism," he said, adding that the grenade appeared aimed toward the Muslim residential district.
Aleo said an investigation was still going on.
It was the latest in a series of blasts in the southern Philippines this month. Twelve people, including a US serviceman, were killed in a series of bombings in Zamboanga City in October.
The Abu Sayyaf, a Muslim kidnapping gang allegedly linked to Osama bin Laden’s al-Qaeda network, has been blamed for the bombings. Five suspects are being held for those blasts.
The military has been waging a massive operation against Abu Sayyaf forces on the predominantly Muslim island of Sulu for months. — Roel Pareño, AFP