Armed assailants have vandalised a United Nations children’s summer camp in central Gaza.

The incident, in which toys were burnt and a guard tied up, follows a similar attack by Palestinian militants on another UN camp in May. There are about 12 UN camps in Gaza, catering for 250,000 children.

In the latest assault more than 20 masked men attempted to set fire to tents and used knives to slash a plastic paddling pool and inflatable slide.

No group has yet claimed responsibility for this attack, but Islamic extremists have repeatedly targeted the UN programme, which involves sports, games and human rights education for the young people of Gaza.

They have accused the UN, which started up the educational scheme in 2007, of corrupting young people.

Hamas, who have control over the Gaza strip, run alternative camps involving military-style marching and Islamic instruction.

John Ging, the local UN chief, described the attack as “cowardly and despicable" and said it was another sign of the urgent need to tackle rising extremism in Gaza.

He promised the site would be rebuilt.

The attack follows Israel’s decision to substantially ease the blockade of Gaza to allow more civilian goods in.

The UN Relief and Works Agency provides services for two thirds of the population of the area.