Tens of thousands of supporters of Shiite cleric Moqtada Al Sadr marched in Baghdad yesterday as a crackdown on his followers raged in southern Iraqi towns and rockets and mortars exploded across the capital.

In Sadr City, the vast Shiite slum named after Sadr's slain father, enormous crowds of angry men jammed the main circle chanting and shouting slogans calling for the ousting of US-backed Shiite Prime Minister Nouri Al Maliki.

"We demand the downfall of the Al Maliki government. It does not represent the people. It represents Bush and Cheney," marcher Hussain Abu Ali said.

The slum of two million people has been locked in a virtual state of siege: "We are trapped in our homes with no water or electricity since yesterday. We can't bathe our children or wash our clothes," said a resident who gave his name as Mohammad.

Mass demonstrations were also held in the northern Kadhimiya and Shula districts. The demonstrations were among the largest anti-government protests Al Maliki's government has faced, although the total number of marchers was impossible to verify.

Cordoned Off

More than 130 people have been killed and hundreds wounded since the government launched a major military operation in the southern city of Basra on Tuesday, targeting districts where Sadr's Mahdi Army militia has a strong presence. Fighting there raged afresh yesterday for a third day. A correspondent in the city said Iraqi forces had cordoned off seven districts but were being repelled by Mahdi Army fighters inside them. Helicopters swooped overhead.

Authorities imposed curfews in other Shiite towns to halt the spread of the violence, which has exposed a deep divide between Shiite parties in Al Maliki's government and Sadr's followers who in many Shiite areas rule the streets.

The government says it is fighting "outlaws." Sadrists say Al Maliki is using military force to marginalise political rivals ahead of local elections due by October.

The clashes have all but wrecked a truce declared last August by Sadr, which US commanders had credited with reducing violence.

Saboteurs blew up one of Iraq's two main oil export pipelines from Basra, cutting at least a third of the exports from the city which provides 80 per cent of government revenue. US oil prices rose more than $1 [Dh3.67] a barrel after the blast.

A massive mortar bombardment struck the main riverside police base at Basra palace before noon yesterday and heavy shooting broke out in a main commercial street in the city.