Jakarta (Agencies) – A powerful exploded at a stand in Merdeka Stadium in Ambon on Thursday, killing three junior high-school students and injuring 11 others, some seriously.

Antara identified two of the dead as Carla P, 15, from State Junior High School (SMPN) 4 and Yoke Siahaya from SMPN 6. Some of the injured are being treated at the GPM Hospital.

The blast occurred at 5:40pm when hundreds of people were exercising at the stadium. It left a gaping hole at the scene.

Ambon, some 2,300 km east of Jakarta, is the main city in the Maluku islands, where a wave of clashes between Muslims and Christians has claimed more than 5,000 lives since early 1999.

Both sides signed a peace deal in February but tension remains high and there has been sporadic violence. A state of civil emergency – one level down from martial law – is still in place in the once scenic area.

However, the situation in Ambon remained relatively peaceful with people continuing to conduct their daily activities unperturbed.