Five American soldiers were killed and three wounded when a suicide bomber blew himself up in the middle of a foot patrol in Baghdad yesterday in the deadliest strike against the US military in the city since last June.

The explosion, along with a rare car bombing outside a hotel in the Kurdish north of Iraq and a suicide blast against a key tribal figure west of Baghdad, came as fears rose of a resurgence in attacks by al-Qaeda after months of relative tranquillity.

The attacks underscored the fragility of a 60 per cent drop in violence across the country at a time when US commanders are studying plans to reduce force levels further after July when more than 20,000 troops will have redeployed.

The suicide bomber walked up to the Americans as they patrolled the upmarket Mansour neighbourhood of west Baghdad yesterday afternoon, detonating his charge outside a clothes shop. An interpreter was injured in the blast along with another nine Iraqis, including a policeman.

Colonel Allen Batschelet, chief of staff of US forces in Baghdad, said: “We remain resolute in our resolve to protect the people of Iraq and kill or capture those who would bring them harm.” Four of the American soldiers were killed outright, while the fifth died later from his injuries.

At least 3,979 American troops have been killed in Iraq since the invasion five years ago. The worst previous single attack on US forces in Baghdad was last June, when a roadside bomb killed five troops.

The overall casualty rate has slowed significantly in recent months, however, in line with the decline in violence, which has been attributed to a surge of 30,000 extra American soldiers and a ceasefire by the powerful Shia al-Mahdi Army.

A decision by Sunni Arab tribes to turn against al-Qaeda and side with US forces is another pivotal factor. Forming civilian security groups, these men work in their own neighbourhoods under the payroll of the US military, but have become a favourite target for extremists wanting to undermine the partnership.

In the latest attack, a female suicide bomber killed a prominent tribal chief who headed such a security unit in the restive province of Diyala. Sheikh Thaeir Ghadhban al-Karkhi’s five-year-old niece, a cousin and a security guard also died.

Al-Qaeda has increasingly used women wearing suicide vests to carry out attacks, in what US officials believe is a sign of desperation.

Violence even shook Iraq’s Kurdish north when a suicide bomber blew up a car packed with explosives outside the luxury Sulaimaniyah Palace Hotel in the normally peaceful city of Sulaimaniyah. Three people were killed and up to 30 were wounded.

American and British commanders have said that they do not believe the recent spate of bombings, such as a twin attack in central Baghdad on Thursday that left 68 people dead, is the start of a wider trend, noting that violence remains down overall.

Referring to Thursday’s double bombings in Karrada, Lieutenant-General Bill Rollo, Britain’s most senior officer in Iraq, said he did not think that the surge policy was at risk.

“I would think so if this was happening on a daily basis but it is not. It stands out I think now more by exception than as the rule,” said the British commander who is based in Baghdad as one of General David Petraeus’s two deputies.

“We and the Iraqis are going to go on trying to drive down the number and level of these attacks as much as we can,” he told The Times in an interview at the weekend.

In a sign of challenges ahead, an American commander warned yesterday that al-Qaeda may be plotting one of its trademark spectacular attacks in Anbar province, a former insurgency stronghold west of Baghdad.

“We have some indicators that they may be planning on executing kind of a large media-type event,” said Major General John Kelly, commander of the I Marine Expeditionary Force in western Iraq. “The good news is we don’t believe they are at liberty to build some of these large bomb-type devices inside the province. They have to kind of import them in.” He added that this raised the chances of any potential attack being foiled by one of the many official Iraqi checkpoints.

General Petraeus, the top US commander in Iraq, and Ryan Crocker, the American Ambassador, are due to present a new report on the country to Washington early next month. Commanders have indicated that it would be best to decide on further cuts after the phased pullout is completed in July.

At present 2,000 US soldiers are being withdrawn from Baghdad under an existing plan to pull out five brigades from Iraq by July 31. A second brigade in the capital is also due to be withdrawn.

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