Denmark shared with Pakistani investigators a video of the suicide car bombing of its embassy in Islamabad, as an Internet posting Thursday purportedly by al-Qaida claimed responsibility and threatened more attacks. The statement, signed by an al-Qaida commander in Afghanistan, said Monday's attack was carried out to fulfill the promise of Osama bin Laden to exact revenge for the reprinting in Danish newspapers of a cartoon of Islam's Prophet Muhammad wearing a bomb-shaped turban. The attack killed six people, including one Danish citizen. It caused widespread destruction and demonstrated the vulnerability of the Pakistani capital to attack by Islamic extremists. The authenticity of the statement, which was posted on a Web site frequently used by Islamic militants, could not be independently verified. It was signed by al-Qaida commander Mustafa Abu al-Yazeed and dated Tuesday. It warned if Denmark fails to apologize for the cartoons, more attacks will follow and Monday's blast will "only be the first drop of rain."