Two grenades exploded at a local championship basketball game at an outdoor court packed with about 1,000 spectators Sunday, killing 27 people and wounding at least 82 others, police said.

A Moslem youth who sped away on a motorcycle was arrested soon after the explosions shortly before midnight Sunday at Dukay district in Esperanza, 600 miles south of Manila and 50 miles southeast of the provincial capital of Cotabato, police said. His identity was withheld.Authorities had yet to determine a motive for the bombing in the region where Moslem separatists and communist guerrillas operate, but a news report suggested it was sparked by heavy betting in the match pitting the hometown team and a visiting squad from nearby Davao city.

Most of those killed were children, said Esperanza police station chief Florencio Balinag.