Four British soldiers and an Iraqi interpreter have been killed by a roadside bomb in Basra, the Ministry of Defence said today.

The five personnel died last night when a convoy of armoured vehicles was blown up by two devices in the northwestern outskirts of the city, which are known to be under the control of Shia militias. The patrol came under simultaneous attack from small-arms fire and rocket-propelled grenades. A fifth soldier was seriously wounded.

“During that attack the five people were killed, all of whom were in the same vehicle. A further soldier who was in the vehicle is very seriously wounded,” said Lieutenant-Colonel Kevin Stratford-Wright, a British military spokesman in Basra. The Iraqi interpreter was a local civilian.

Witnesses said that the British patrol had earlier repulsed an attack by five gunmen in a different district of the city, wounding one of the attackers. During the second ambush, British forces returned fire while trying to evacuate the wounded.

The ambush took place in Hayaniya, a slum stronghold of the al-Mahdi Army, the militia loyal to the radical Shia leader, Hojatoleslam Moqtada al-Sadr.

The militia is struggling to take control of Iraq's second largest city as British forces prepare to pull out, engaging in tit-for-tat attacks with the secular Fadhila party presently in charge of the local government.

One resident told Reuters that he had seen at least one armoured vehicle on fire, believed to be a Warrior infantry fighting vehicle.

“We heard two explosions that shook the house. I went out and saw one armoured vehicle that was completely destroyed and another with less damage. I saw some soldiers being taken away, but I don’t know how many,” he said, declining to give his name.

Photographs of the scene this morning showed a large crater in the road that was at least a metre deep and several metres wide and Iraqi children taking away pieces of burned wreckage.

After the attack, a British patrol was seen storming an Iraqi checkpoint close to the scene of and disarming the police there. The casualties bring to six the number of British soldiers killed in Basra since Sunday, making it one of the deadliest weeks of the Iraq war for UK forces. A total of 140 British military personnel have died in Iraq since the invasion in 2003.

Kingsman Danny John Wilson, aged 28, of the 2nd Battalion, The Duke of Lancaster's Regiment, died after suffering injuries on a routine patrol in Basra on Sunday. The following day, Rifleman Aaron Lincoln, of the 2nd Battalion, The Rifles, also shot in the city. He was 18.

In February, Tony Blair announced that 1,600 troops would be pulled out of the province this summer after the successful completion of six-month operation to bring the security situation under control. Speaking today, as the 15 British sailors and mariens seized by Iran returned to London, he said the Basra attack was a reminder of the "sober and ugly reality" of daily violence in Iraq.

“Just as we rejoice at the return of our 15 personnel, so today we also grieve and mourn for the loss of our soldiers in Basra who were killed as a result of a terrorist act,” he said.

A British military spokesman in Basra confirmed initially that there had been a “serious incident” in the night. This morning the MoD released a statement confirming the deaths.

"It is with deep regret that the Ministry of Defence must confirm that four British soldiers and a civilian interpreter have been killed in Iraq today, 5 April 2007. The five were killed in a roadside bomb attack against a Warrior patrol west of Basra this morning."

"Next of kin are being informed and no further details will be released until this process is complete."

Today's attack will place fresh scrutiny on the British handover of Basra later this summer. In February, Mr Blair conceded that "Basra is how we want it to be" but said that the transfer of authority to Iraqi control had been made possible by successful reconstruction projects and Operation Sinbad, in which British and Iraqi forces removed insurgent hotspots from the province.

Yesterday the Iraqi Prime Minister, Nouri al-Maliki, confirmed that another British-controlled province, Maysan, would be handed over to Iraqi authority later this month.

The US military reported today that six American soldiers have been killed in separate ambushes and bomb attacks in Baghdad on Wednesday. US commanders said they were also looking into reports that a Black Hawk helicopter had been brought down south of Baghdad.

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