The raid lasted about 30 minutes and ended peacefully

They demanded an apology from Denmark and Norway over the publication of cartoons of the Prophet Muhammad that have offended Muslims.

One of the gunmen said citizens of both countries should not enter Gaza until the apology is made.

The cartoons first appeared in September in the Danish newspaper Jyllands-Posten and were later reprinted in a Norwegian paper.

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Some of the cartoons depict Muhammad as a terrorist. One image depicts the prophet wearing a turban shaped as a bomb with a burning fuse.

Islam bans any depiction of Muhammad or Allah, in case they lead to idolatry.

The cartoons have sparked protests, flag burning and calls for boycotts of Danish products across the Islamic world.

On Monday, about 15 gunmen burst into the EU office in Gaza City, and withdrew about 30 minutes later. No shots were fired, and there were no reports of injuries.

The al-Aqsa Martyrs' Brigades said they carried out the raid.

Danish regret

Copenhagen has expressed regret for the furore over the cartoons, but refused to get involved, citing freedom of expression. "The government can in no way influence the media," Prime Minister Anders Fogh Rasmussen said on Sunday.

"And the Danish government and the Danish nation as such cannot be held responsible for what is published in independent media," he added.

The newspaper that published the cartoons, Jyllands-Posten, has said earlier it published the drawings to test the boundaries of expression about Islam.

Its editorial on Sunday said it did not mean to insult Islam.

"We at Jyllands-Posten feel regret because the issue has reached this level and we reiterate that we did not mean to insult anybody," it said. "We believe, like the rest of Danish society, in the respect of freedom of religion."