JOLO: Officials say a man lobbed a grenade at a store in the southern Philippines, killing four people and wounding 23 in an attack that appears to be unrelated to terrorism.

Army Colonel Cirilito Sobejana says the attacker was arrested following the late Saturday grenade blast in Busbus village near the airport in Sulu province's Jolo town.

The motive for the attack wasn't immediately clear, but a military officer said Sunday that the attacker, who was identified by police as Sedimar Rabbah, returned to the area to retaliate after being beaten by a group of men who accused him of stealing a cellphone.

Aside from kidnappings for ransom and killings by Abu Sayyaf extremists, predominantly Muslim Sulu has long been troubled by a large number of illegal guns and other weapons.