Iraqi and U.S. forces sweep through Iraqi city of Diwaniya

In Ramadi, west of Baghdad, a chlorine truck bomb killed at least five people and wounded 15, three police officers said of the latest attack involving the poisonous chemical. Iraqi police Colonel Tareq al-Dulaimi said 15 were killed.

The government said this week it was extending Operation Imposing Law, a major security crackdown in Baghdad, to other cities.

While the operation has succeeded in reducing the death rate in Baghdad, the government says militants forced out of the capital have turned other areas into new "killing fields".

An Iraqi security source said Iraqi and U.S. troops fought militiamen in southeast Diwaniya, a stronghold of Sadr's Mehdi Army which is accused by Washington of helping to drive Iraq towards civil war through attacks on Sunni Muslims.

A hospital in Diwaniya, 180 km (110 miles) south of Baghdad, said at least one person had been killed and 15 wounded. A Mehdi Army leader said six women and children were wounded when a U.S. helicopter fired on a hostel in the city. There was no independent confirmation of the report.

"Iraqi army soldiers swept into the city of Diwaniya early this morning to disrupt militia activity and return security and stability of the volatile city back to the government of Iraq," the U.S. military said in a statement.

Sadr is a key political ally of Shi'ite Prime Minister Nuri al-Maliki. But the United States regards his Mehdi militia as the greatest threat to peace in Iraq.

POLICE STAY AT HOME

The Iraqi security source told Reuters that all police in Diwaniya, who are suspected of being infiltrated by Mehdi Army militia, had been ordered to stay at home.

"There were clear instructions for local police not to report to work today. The security forces are from outside the city," the source said.

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