(AP) Masked gunmen on Monday briefly took over a European Union office to protest a Danish newspaper's publication of cartoons deemed insulting to Islam's Prophet Muhammad, the latest in a wave of violent denunciations of the caricatures across the Islamic world.

The gunmen demanded an apology from Denmark and Norway, and said citizens of the two countries would be prevented from entering the Gaza Strip.

"We are calling on the citizens of the two countries to take this threat seriously because our cells are ready to implement this all over Gaza," one militant said.

The 12 drawings _ published in September by the Danish newspaper Jyllands-Posten and republished in a Norwegian paper this month _ included an image of the prophet wearing a turban shaped as a bomb with a burning fuse. Islamic tradition bars any depiction of the prophet, even respectful ones, out of concern that such images could lead to idolatry.

The cartoons have touched off protests, flag burnings and boycotts of Danish products throughout the Muslim world. On Sunday, Palestinian protesters burned Danish flags in two West Bank towns.

In Monday's violence, the gunmen burst into the EU office, then withdrew several minutes later. A group of about 15 masked men, armed with hand grenades, automatic weapons and anti-tank launchers, remained outside, keeping the offices closed. No shots were fired, and there were no reports of injuries.

The gunmen left the building after about half an hour.

The Al Aqsa Martyrs' Brigades, a violent group linked to Palestinian leader Mahmoud Abbas' Fatah Party, claimed responsibility. Al Aqsa has been involved in much of the recent chaos plaguing Gaza.

Jyllands-Posten has refused to apologize for the drawings, citing freedom of speech. The drawings were reprinted on Jan. 10 by Norwegian evangelical newspaper Magazinet in the name of defending free expression, renewing Muslim anger.