Nine American soldiers were killed and 20 injured when two lorries exploded in quick succession at the entrance to their base in a province north of Baghdad yesterday.

The first lorry hit the concrete checkpoint barriers surrounding the US outpost and exploded after the troops opened fire. Then a second lorry rammed into the wreckage, dragging it and other rubble about 30 metres before that driver, too, detonated his payload as he came under heavy fire, the US military said.

The bombing, which was claimed by an insurgent group linked to al-Qaeda, occurred in Diyala, fast becoming one of the deadliest regions in the country.

Successful efforts by the US forces and Iraqi leaders to turn tribes in the Sunni Triangle against al-Qaeda have driven many of the terrorists to Diyala, a region of palm groves and farms ideally suited to guerrilla warfare.

Washington is sending more than 20,000 extra troops into the capital and the Sunni Triangle to prevent Baghdad slipping entirely out of control. In response, insurgent groups have focused their efforts on other parts of the country, while still sending suicide bombers into the city’s markets.

In Baquba, close to where the outpost was attacked, gunmen dressed as Iraqi police killed six people, while in a village south of Baghdad masked assailants killed seven members of the same family. “We can’t find any reason for these killings. It’s meant to drive a wedge between Shia and Sunnis, that’s all,” a police officer said.

The cycle of violence has been stepped up after a brief lull that followed the start of the US troop “surge” two months ago, as insurgents appeared to be reassessing their tactic of how best to foment sectarian war in the country.

American opponents of the surge are pointing to the relentless killings as evidence that President Bush’s last-ditch effort to save Iraq is failing.

“While violence against Iraqis is down in some Baghdad neighbourhoods where we have ‘surged’ forces, it is up dramatically in the belt ringing Baghdad,” Senator Joe Biden, the chairman of the Senate Foreign Relations Committee and a Democratic presidential hopeful, wrote in an article this week. “The civilian death toll increased 15 per cent from February to March. Essentially, when we squeeze the water balloon in one place, it bulges somewhere else.”

Senator Biden pointed to the northern city of Tal Afar as an example of the problems of the US strategy in Iraq. After a big US operation in 2005 to expel insurgents, Tal Afar was hailed last year by President Bush as a “free city that gives reason for hope in a free Iraq”. That image was shattered last month when Iraqi police and Shia militiamen of the Mahdi Army bound and summarily killed scores of Sunni men in revenge for a suicide lorry bombing that killed more than 70 people in the town market.

“I know of 200 families who have fled. If Bush said that this is the best example, why have all these families left?” said Abu Hassan, a resident of the town who was too scared to give his full name after losing two friends in the police and militia rampage. He said that the Iraqi Army had taken charge of the Sunni part of town, but that police and militiamen were still running the Shia areas, and occasional killings continued.

Before last month’s bombing, Sunnis were receiving death threats from Shia militias to leave the town. Now, though, according to the International Organisation for Migration, militias are trying to prevent them leaving mixed areas for fear that terrorists will use chemical bombs against Shia districts.

Shia families, on the other hand, are also trying to leave, but face danger from Sunni insurgents in the areas surrounding the town. “This is not the best example, it is the worst,” Abu Hassan said, vowing never to return.

Counting the cost

3,332 US deaths 20.03.2003 to 24.04.07 — an average of more than two a day

145 UK troops and 125 from other coalition forces have been killed over the same period

24,314 members of the US forces have been wounded

37 US troops killed on January 26, 2005 — the costliest day of the conflict

137 killed in November 2004, the costliest month for the US

90% of casualties in Iraq survive; 69.7% in the Second World War; 76.4% in Vietnam

Source: icasualties.org; US Department of Defence

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