Al-Qaida-led Iraqi insurgents issued a video Thursday purporting to show the killing of 20 kidnapped Iraqi police and soldiers, each shot in the head execution-style as they knelt in a row. The video showed a masked gunman walking down the row of captives, who were blindfolded with hands bound behind their backs. He shot them one by one, sending each tumbling forward as two other masked militants walked alongside him, carrying a black banner of the Islamic State of Iraq. The Islamic State of Iraq, a coalition of Sunni insurgents incluiding al-Qaida in Iraq, claimed on Saturday to have abducted the 20 and threatened to kill them after 48 hours unless the government freed female prisoners and handed over police accused of a rape. The authenticity of the six-minute video could not be independently confirmed. It was posted on an Islamic militant Web forum where the Islamic State of Iraq has issued previous videos.