The powerful Shia cleric, Hojatoleslam Moqtada al-Sadr, resurfaced in Iraq today to give an angry, anti-American sermon and raise questions about the intentions he holds for his radical, sectarian movement.

Hours later, the commander of his feared al-Mahdi Army militia in Basra was reported killed by British and Iraqi soldiers, raising tensions in the city, which is already in the grip of competing militias as it nears handover to full Iraqi control.

Witnesses said Wissam al-Waili, more widely known as Abu Qader, was shot in his car as left Friday prayers in Basra. A British military spokesman said he was killed by Iraqi special forces but local police said it was a British operation.

A spokesman for the al-Madhi Army said it was unclear who was responsible but threatened "political resistance". Reports from Basra said the city was in a tense state, with armed men on the street, even though Abu Qader's precise role was disputed.

Recent reports from the city said that he had been suspended from the al-Mahdi Army for leading a splinter group in clashes with Fadhila, the other main Shia movement that controls much of the provincial government. A British military statement identified him just as a "militia leader" wanted for political assassinations, gun smuggling and attacks on UK forces.

Abu Qader's death coincided with the reappearance of Hojatoleslam Moqtada al-Sadr, one of the most polarising and recognisable figures in Iraq's traumatised political landscape, after a four-month absence.

Six months ago, his al-Mahdi Army was identified by the Pentagon late last year as an even graver threat than al-Qaeda to the stability of Iraq because of its death squads and grip on various arms on the Iraqi Government.

But during the joint US and Iraqi security crackdown this year, it has largely disappeared from view, with reports that it was splintering as it waited for the military operation to run its course.

Sectarian murders in Baghdad have fallen from 1,400 in January to 500 during the same period, while Hojatoleslam al-Sadr crossed into Iran, where his Shia movement has extensive support. Yesterday US intelligence officials told The New York Times that he had slipped back across the border to his house in the holy Shia city of Kufa.

At Friday prayers, the 33-year-old cleric, whose face plasters walls in Shia neigbourhoods across Iraq, duly appeared and led his supporters in anti-American chants. "No, no for Satan. No, no for America. No, no for the occupation. No, no for Israel," he called at the start of his speech.

The roughly 6,000 worshippers in the mosque echoed his chants and listened as he said that “the occupation forces should leave Iraq,” and condemned fighting between his al-Mahdi Army militia and Iraqi security forces, saying it “served the interests of the occupiers".

Iraq analysts say that the al-Mahdi Army, which maintains a bloc of 30 MPs in the Iraqi parliament, despite a rash of recent high-profile resignations, is feeling the strain of a division between the most radical fringes, which hope to deepen the country's sectarian conflict, and those who believe the movement should contribute to the Iraqi Government's plan for national reconciliation.

There is no clear reason why Hojatoleslam al-Sadr should have re-appeared now, other than re-assert control of his followers, although there is speculation that he is keen to take advantage of the illness of one of his chief rivals, Abdul-Aziz al-Hakim, the leader of the Supreme Islamic Council of Iraq (SCIRI), who has recently been forced to go to Iran for lung cancer treatment.

As Hojatoleslam al-Sadr prepared to speak in Kufa, insurgents in Baghdad defied the traffic ban that precedes Friday prayers in the capital to blow a hole a bridge linking two Sunni districts in the west of the city. The bridge was left standing but severely damaged. The attack follows the near-destruction of the Sarafiya bridge, one of Baghdad's iconic structures and key crossing over the Tigris, last month.

The US military announced the deaths of six soldiers this week and continued its massive search for two soldiers taken hostage in an ambush claimed by al-Qaeda last month. Trawling through swamps in hostile territory south of Baghdad, thousands of troops are looking for the two men after the body of the third, Private Joseph Anzack Jr, was pulled from the Euphrates River and identified on Wednesday.

Of the six deaths confirmed today, five occurred yesterday in separate shootings and roadside bombings, which remain the leading cause of US military casualties. The sixth soldier died in a bombing in Tikrit, 175 km (110 miles) north of Baghdad, on Tuesday. Around 90 US troops have died in May so far, raising the possibility that it will eclipse April as the deadliest month of the year so far.

US commanders say the high casualty rate is the consequence of the confrontational tactics of security crackdown and the use of smaller, more advanced bases, where troops are more vulnerable to attack. Yesterday President Bush predicted further spectacular attacks designed to further weaken American support for the war, which is at an all-time low, over the summer. “It could be a bloody -- it could be a very difficult August,” he said.

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