SYDNEY, Australia — Five teenagers brandishing baseball bats and machetes rampaged through a suburban Sydney school Monday and hit a teacher over the head, police said. Eighteen students were treated for minor injuries.

The drama unfolded as hundreds attended an assembly in an outdoor area of Merrylands High School.

As the attackers moved in, teachers rushed the students back to class, where they sought refuge behind locked doors, under desks, even in a cupboard.

The teens, between the ages of 14 and 16, were arrested and will appear in court Tuesday to face more than 100 charges, police said. They have been charged with offenses including assault and malicious damage and could face up to seven years in prison if convicted.

Police refused to say whether the teens were students at the school.

Some students reported the gang was armed with two machetes.

BAGHDAD — Iraqi government forces and Shiite militia fighters clashed anew today despite a government ultimatum to anti-American cleric Muqtada al-Sadr to either disband his Mahdi Army or give up politics.A U.S. soldier died Tuesday from wounds received in a roadside explosion the night before in northeast Baghdad, raising to 11 the number of American troop deaths since Sunday.Al-Sadr's aides said Monday that he would only dismantle the powerful militia — estimated at up to 60,000 — if ordered by top Shiite clerics, who have remained silent throughout the increasingly dangerous showdown.Al-Sadr is threatening to formally end the freeze he imposed seven months ago on his Mahdi Army fighters.