US troops battle Iraqi militants in Basra

US forces were drawn deeper into Iraq's four-day-old crackdown on Shia militants today after launching air strikes in the country’s second city, Basra, and battling militants in Baghdad.

The fighting has exposed a rift within the majority Shia community and put pressure on Prime Minister Nuri al-Maliki, whose forces have failed to drive fighters loyal to cleric Moqtada al-Sadr off the streets Basra.

Prime Minister Nuri al-Maliki, who had given the Basra militants 72 hours to surrender, extended the deadline for them to turn in their weapons in exchange for cash until April 8th.

The government says it is fighting "outlaws", but Mr al Sadr's followers say political parties in Mr Maliki's Shia-led government are using military force to marginalise their rivals ahead of local elections due by October.

Television footage from Basra showed masked gunmen from Mr al Sadr's Mehdi Army still in control of the streets, armed with rocket launchers and machine guns.

The fighting has trapped Basra residents in their homes. The United Nations said it was standing by with blood bags, trauma kits, 200 tonnes of emergency food and 39 million water purification tablets.

In Baghdad, there were clashes in at least 13 mainly Shia neighbourhoods, especially Sadr City, the vast slum named after the cleric's slain father and his main power base.

Authorities announced a curfew in Baghdad, but rocket attacks and clashes continued. One missile hit the Green Zone office of Vice President Tareq al-Hashemi, killing a security guard.

Meanwhile charges were dismissed today against one of eight US Marines originally accused of involvement in the shooting death of two dozen unarmed Iraqi men, women and children at Haditha. The charges of involuntary manslaughter against Lance Cpl. Stephen B. Tatum were dismissed "in order to continue to pursue the truth seeking process into the Haditha incident," the Marines said in a written statement.