The "final battle for Basra" began with deafening blasts at 4.58am as units of the Iraqi army moved into al-Tamiyah, a district under the control of Muqtada al-Sadr's Mehdi Army.
Commandos who had just finished a six-day course in house-to-house fighting given by British troops at the Shaiba base, near Basra, targeted a group of six buildings used as headquarters by the militia.
The Independent revealed last week that the Iraqi commander in charge of security for the south, General Mohan al-Furayji, was planning a campaign against Shia militias in the city.
The operation, called Saulat al-Fursan (the charge of the knights) is believed to be one of several planned to clear Basra of militias before provincial elections planned for the autumn. Up to 90 casualties were taken to local hospitals in ambulances, private cars and taxis. At the city's general hospital, Dr Ali Mahmud said: "We cannot take any more as we don't have enough equipment or enough medicine. If casualties continue we will have to move them outside the city."
Basra and southern Iraq account for 90 per cent of state revenue and 70 per cent of Iraq's known oil reserves.
The Prime Minister, Nouri al-Maliki, who described the region as the "lung of Iraq", said during a flying visit to the city yesterday: "We had to do this because Basra was experiencing a brutal campaign from internal and external gangs targeting its security and stability... Basra has become a place where civilians cannot even secure their lives and property."
British forces did not enter Basra city during yesterday's operation.