The security sources and school officials said the militants detonated three explosive devices in two of the buildings of the school in the northern Gaza Strip. The blast occurred before the start of the school day and no one was injured in the attack.
The sources added that the assailants had stormed the school, handcuffed its guards and set off explosive devices after moving the nightwatchmen several metres away from the building.
The explosions, which took place at 4 am, caused a fire that burnt most of the furniture at Gaza's only international school.
"A large number of masked gunmen attacked the school at dawn. They poured petrol all around and blew up several explosive devices and destroyed some of the premises," said Rebhi Salem, the school's director.
The gunmen identified themselves as an al Qaeda organization operating in Gaza, Salem said. There have been a rash of attacks in Gaza in recent months attributed to Islamist groups that claim to be followers of al Qaeda.
The school is a private institution that is part of an association of "American Schools" in the Middle East. The
curriculum stresses English as well as Arabic studies. None of the teachers are American.
A U.S. embassy official said the school has no connection to the U.S. government.
The school, located near the former Jewish settlement of Dugit, has been a target before. Two teachers were
kidnapped from the school by gunmen in 2006 and the school was repeatedly hit by Israeli fire during the past few years of Israeli-Palestinian fighting.
Salem said growing violence in Gaza has prompted most foreign educators to leave the strip for their own safety.