Early today, 2 dozen masked and armed men invaded a UN kids' summer camp in Gaza, tied up an unarmed guard, burned and slashed tents and a perimeter fence and also slashed a plastic swimming pool, slide and other accoutrements.

The UN's summer activities programme for 250,000 children has been criticised by Islamists for corrupting youth. Its main rival is Hamas camps, dedicated to Islamic study, parades and athletics, which Hamas says have 100,000 attendees.

John Ging, local UN head, called the attack "cowardly and despicable" and said it was the latest sign of growing levels of extremism in Gaza. He said it gives further evidence "of the urgency to change the circumstances on the ground that are generating such extremism."