Although it was initially declared that four had died, the death of a fifth serviceman was made public after immediate family of all five had been informed.

The Ministry of Defence did not release names of the dead servicemen, or the mission in which they were involved. It remained unclear why it took so long to confirm the number of dead.

The Lynx Mark 7 helicopter, one of about nine flying regular patrols in southern Iraq, is believed to have been brought down on Saturday by a rocket-propelled grenade fired from up to 300 yards away by a gunman who got a lucky shot.

There were also different accounts of how a number of “civilians” were killed in the consequent confrontation between soldiers from the 1st Battalion The Light Infantry who arrived at the scene of the crashed helicopter, and a crowd of Iraqis who attacked them with blast bombs, stones, petrol bombs, and opened fire with AK47 Kalashnikov rifles.

The Iraqi police said that five civilians, including two children, died from bullet wounds.

The British Army said that it had fired plastic baton rounds at the crowd, and then had to resort to live rounds, although only three were fired.

Des Browne, the Defence Secretary, will make a statement on the crash in the Commons today.

Yesterday he argued that fewer than 300 people had taken part in the clashes in Basra, and that they had been brought under control within hours. “It is not an indication of the state of Basra,” he insisted.

As a curfew was imposed for the second consecutive night in Iraq’s second city, relatives of the dead Iraqis accused British troops of opening fire on gangs of youths celebrating the helicopter crash.

But British military commanders said that the deaths were caused by militants who had used the crowd as human shields as they attacked the British troops.

They said that the militants had also fired mortars and blast bombs at the rescuers and local firemen, and shrapnel is believed to have caused many of the injuries to 45 civilians, some of whom were children.

Members of al-Mahdi Army, the militia which supports the radical Muslim cleric Hojatoleslam Moqtada al-Sadr, were being blamed for the attack on the helicopter and the subsequent assault on the British troops. Two armoured vehicles were set on fire and several British soldiers received minor injuries.

The attack on the Lynx was the first time that a British helicopter had been shot down in Iraq since Operation Telic began in March 2003. Military commanders in southern Iraq rarely use the Lynx to ferry troops, reserving it for routine trips, often with media or VIP visitors, or for surveillance.

As the British Army investigators began examining the wrecked helicopter, which crashed in a residential neighbourhood, Iraqi police chiefs in Basra said that they wanted to interview locals who claimed to have seen the rocket attack by Islamic militants.

The suspected weapon, an RPG7, is light enough to be carried and fired by a single operator. The Lynx is equipped with special defensive systems to evade heat-seeking surface-to-air missiles, such as chaff and flares to confuse an oncoming missile. But it is vulnerable to rocket-propelled grenades and has no system to evade such an attack other than through tactical flying.

Residents told The Times that they had noticed the Lynx swooping over the relatively affluent suburb that is close to the local governor’s residence.

Major-General John Cooper, commander of the Multinational Force Southeast based in Basra, praised the efforts of local Iraqi police and soldiers for helping to restore calm after the fierce confrontation. A curfew was imposed by the Basra provincial council.

President Talabani sent a message of condolence to Tony Blair, condemning what he called a “vile crime”. He added: “I can assure you that Iraqis continue to honour and appreciate the efforts and sacrifice made by Her Majesty’s forces, first in our liberation from the unspeakable tyranny of the Saddamist dictatorship and then in laying the foundations for a peaceful and democratic Iraq.”

A senior police officer in Basra said he hoped that the British commanders would co-operate with their investigation into the five civilian deaths. Local politicians have previously clashed with British commanders over their refusal to allow soldiers to be interviewed after violent incidents.

• A US Marine was killed in fighting yesterday in the western province of Anbar, bringing the US death toll since the 2003 invasion to 2,416.

ONE DAY’S TOLL

May 7th 2006

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