He said half of them are now back and are followers of Sepah-e-Sehaba, a Sunni sectarian group with a history of attacking Shiites.

Sunni insurgents started attacking Shiites, who make up about 60 percent of all Iraqis, to destabilize the new Iraqi government.

Shiite death squads in Baghdad have forced many Sunnis to flee to Baquba, 35 miles to the north, where some have joined the insurgency and have begun attacking Shiites.

In the northern areas of Pakistan, such as Parachinar and Gilgit-Baltistan, Muslim mitants have continuously been attacking and killing Shiites.

These patrols were authorized by the United Nations to enforce no-flight zones to prevent Iraq's air forces from attacking Shiites in the south and Kurds in the north.

The Shiite leaders said they feared insurgents might manipulate the vote by attacking Shiites to keep them away from the polls.

In recent days, several terrorist groups had vowed to avenge allies killed in Tal Afar, and one warning issued by Al Qaeda in Mesopotamia had pledged specifically to attack Shiites.

The Iraqi military later used helicopters to attack and kill Shiites.

In the south, government forces bombarded the Holy Places of Najaf and Karbala, later attacking Shiites who had taken refuge in the marshes north of Basrah.

The same month, a letter allegedly written by al-Zawahiri (later rejected as a "fake" by AQI) appeared to question the insurgents' tactic of indiscriminately attacking Shiites in Iraq.