Abu Musab al-Zarqawi has vowed to kill anyone who participated in the referendum vote. Last month, the Jordanian-born Sunni extremist went even further, declaring an all-out war to kill Iraq's majority Shi'ite Muslims.
During January parliamentary elections, Zarqawi, who opposes Iraq's political process because he believes it is un-Islamic, said that it carried out at least nine suicide bombings at or near polling sites. The violence killed more than two dozen people.
Al-Qaida's warning not to take part in elections prevented many Sunni Arabs from voting in the country's first democratic elections. But millions of Shi'ites defied the threat and voted, giving them an overwhelming majority in the new government.