ZAMBOANGA CITY, Philippines?Two revelers were killed and 15 others wounded in a grenade attack on a village carnival in part of the southern Philippines known for Islamist violence, the military said Thursday.

The motive of the attack just before midnight Wednesday near Luuk town on Jolo island was unknown, and no group has claimed responsibility, said Major David Hontiveros, military spokesman for the southwestern Philippines.

The 17 casualties were all hit by shrapnel, he told reporters.

Jolo is a mainly Muslim stronghold of the Abu Sayyaf group, which has bombed or kidnapped Christian or Western targets across the southern Philippines for the past 20 years.