At least 20 killed as rebel cleric's Mahdi militia battles Iraqi troops for control on streets of Basra

IRAQI forces yesterday faced their toughest challenge since taking over security in Basra from British troops, battling with Shiite militia for control of the southern oil port.

The violence, in which at least 20 people died, was part of an escalating confrontation between the Iraqi government and Shiite cleric Muqtada al-Sadr's followers.

About 4,100 British troops are still based outside the city at its airport although they were not involved in yesterday's operation.

Sadr declared a unilateral ceasefire last August which, along with a US troop building and a Sunni alliance with the American forces, has contributed to a steep drop in violence over the recent months.

But the truce frayed as Sadr's allies grew increasingly angry over US and Iraqi raids and detentions and demanded the release of followers rounded up in recent weeks.

The cleric recently told his followers that although the truce remains in effect, they were free to defend themselves against attacks.

Sadr's headquarters in Najaf also ordered field commanders with his al-Mahdi army militia to go on maximum alert and prepare "to strike the occupiers" – a term used to describe US forces – and their Iraqi allies.

Politicians from Sadr's movement announced in a Baghdad press conference that a civil disobedience campaign – which began in selected districts of the capital and included the closure of businesses and schools – was being expanded across the country.

Stores and schools were closed in several other predominantly Shiite neighbourhoods in the capital, apparently in compliance with the civil disobedience order. Armed Mahdi army members were seen patrolling the streets in some Shiite neighbourhoods of the capital.

Formed after Saddam Hussein's overthrow in April 2003, the Mahdi army is loyal to Sadr, a fiercely outspoken cleric who is popular among Iraq's poor, urban Shiite majority.

Sadr led rebellions against US-led forces in 2004. In August 2004 the army took refuge in Iraq's holiest Shiite shrine, the Imam Ali Mosque in Najaf, during fighting with US forces. A three-week siege was ended after a compromise under which the Shiite militiamen agreed to leave the shrine and US forces pulled out of the city.

Since the bombing of the Golden Mosque in Samarra unleashed a wave of sectarian bloodletting in February 2006, the Mahdi army has grown more powerful. Sunni Arab leaders and US officials blamed it for death squad killings.

Sadr ordered the Mahdi army to freeze its activities for six months in August 2007 after gun battles among rival Shiite factions killed dozens of people in the holy city of Kerbala. Sadr undertook the move to weed out rogue elements which have splintered from the militia and to reassert his control. He extended the ceasefire by six months on 22 February.

The fighting yesterday erupted a day after prime minister Nouri al-Maliki flew to Basra and announced the security crackdown against the militias.

Iraq's second-largest city accounts for most of its oil exports, but an oil ministry official said production and exports had not been affected by the fighting.

Curfews were also imposed in the Shiite cities of Kut, where a large number of Mahdi army gunmen were seen deploying on the streets, and Nasiriyah.

In Baghdad, suspected Mahdi army gunmen exchanged gunfire with security guards of the rival Shiite Supreme Islamic Iraqi Council.

Security in Basra had been steadilty declining well before Britain handed over security to the Iraqis on 16 December.

INQUIRY 'WILL MAKE SURE IRAQ WAR MISTAKES ARE NOT REPEATED'

AN INQUIRY into the Iraq war is needed to ensure mistakes are not repeated while British forces remain in the country, the Tories said yesterday.

William Hague, the shadow foreign secretary said that the war, which began in 2003, had almost lasted as long as the Second World War, and that the case for a Privy Council inquiry was now overwhelming. An inquiry would also inform operations in Afghanistan, he said.

However, the government repeated its belief that an inquiry would be premature while UK troops remained in Iraq.

Around 4,200 troops are in the country and plans to begin a phased withdrawal in spring appear to have slipped.

Mr Hague said that while the initial 23-day operation to invade Iraq and topple Saddam Hussein had been successful, the government's failure to plan for post-war reconstruction and the outbreak of civil war had been disastrous, and 175 British troops had lost their lives.

He said a delay would mean asking key players to give evidence – and find documents – after almost a decade.

Mr Hague added: "What is proposed here is not a trial or impeachment. It is an effort to learn for the future, for those of us who voted for or against the war in Iraq.

"The need to learn from what has happened is serious and urgent."