Multiple explosions shake a mosque in an Indonesian high school, 55 injured

Multiple explosions shook a mosque at a high school during Friday prayers in Jakarta, Indonesia's capital, injuring at least 55 people, mostly students, police said.

Witnesses told local television stations that they heard at least two loud blasts around midday, just as the sermon had started at the mosque at SMA 27, a state high school within a navy compound in Jakarta's northern Kelapa Gading neighbourhood. Students and others ran out in panic as grey smoke filled the mosque.

The suspected perpetrator of an explosion at a mosque in a school complex in Indonesia's capital was about 17 years old and was currently undergoing surgery, the country's deputy house speaker said on Friday.

Sufmi Dasco Ahmad spoke to reporters after visiting the hospital treating the victims.

Jakarta city police chief Asep Edi Suheri told reporters there was an explosion "in the vicinity" of a high school and that 55 people had been admitted to hospitals with a range of minor to serious injuries, including burns from the blast at the mosque inside a school complex in the Kelapa Gading area.

An investigation was underway, police said.

The cause of the blasts was not immediately known, but they came from near the mosque's loudspeaker, according to Jakarta Police Chief Asep Edi Suheri.

People were rushed to nearby hospitals. Some were soon sent home, but 20 students remain in hospital care, three of them with serious injuries, the police chief said.

Suheri said an anti-bomb squad that was deployed at the scene found toy rifles and a toy gun near the mosque.

"Police are still investigating the scene to determine the cause of the blasts," Suheri said, and urged against speculation that the incident was an attack before the police investigation is completed.

"Let the authorities work first," Suheri said. "We will convey whatever the results are to the public."