The purported leader of an Al Qaeda-dominated insurgent umbrella group in Iraq has called for the murder of all members of the country's main Sunni Arab political party, in an audio message posted Tuesday on militant Web sites.

Abu Omar al-Baghdadi, leader of the Islamic State in Iraq, said in the half hour audio message that members of the Iraqi Islamic Party had 15 days to repent, but its leaders should be killed immediately.

"We hereby declare the Islamic Party, with all its tendencies, its leadership and its members to be an enemy of God and his prophet," he said. "It is a sect of apostasy which should be killed wherever its members are found."

Al-Baghdadi singled out five leaders to be killed immediately, including Iraqi Vice President Tariq al-Hashemi. He promised an unspecified reward for their deaths.

The comments appeared designed to tap into opposition to the Iraqi Islamic Party, the main Sunni political faction in parliament, which is locked in a bitter power struggle with Sunni groups that turned against Al Qaeda in Anbar province and elsewhere.

Those Sunnis, organized in awakening councils, believe they deserve power at the expense of the Islamic party, which is part of the Shiite-led government.

The awakening councils have been key in beating back Al Qaeda in Iraq and restoring a measure of calm to large swathes of the country. In April, al-Baghdadi issued another audio message calling on the councils to return to the insurgency.

The U.S. has described al-Baghdadi, who has never been seen and only issues audio messages, as a fictitious character used to give an Iraqi face to an organization dominated by foreign Al Qaeda fighters.

In his message, al-Baghdadi also urged the people of Diyala province to continue fighting government and U.S. troops.

"Be faithful men and fight on," he said. "We promise you the days of the occupiers are numbered and we are at the doorstep of victory." Throughout the tape, he referred to the Shiite-dominated government as followers of Iran.

A largely mixed ethnic and sectarian province, Diyala has been the scene of some of the fiercest fighting in the country and remains a center of operations for Al Qaeda in Iraq.