The country's most feared group, headed by Abu Mussab al-Zarqawi, announced in a statement on an Islamist website that it carried out the slaughter.

Most of the recruits were found strewn out along the road with a single gunshot to the heads in one of the deadliest attacks against the country's fledgling security forces.

"The bodies of 37 new recruits, some with their hands tied, were found, shot dead, on the side of the road, while the corpses of 12 others were found in a minibus a few metres away that had been burnt out," said a spokesman for the interior ministry, Colonel Adnan Abdul Rahman.

"The recruits, who came from all over the southern provinces of Iraq, were mainly Shiite and were returning home on board three buses when they were ambushed in Diyala province," he told AFP.

The attack happened on Saturday afternoon after the recruits completed a training course on a base outside the town of Mandali in eastern Iraq, Mandali's Iraqi national guard commander Ali al-Kaaki said.

He put the toll at 48, but his figure included five civilians who were drivers.

"This was an execution. We found the dead lying face down by the roadside with a single bullet wound to the head," Kaaki said, adding that the recruits were wearing civilian clothing and were unarmed at the time of the attack.

Two of the minibuses were torched by the assailants and they made away with the remaining vehicles, according to Kaaki, who said five buses had been used.

He added that the victims had all their money and personal affairs on them but were missing their shoes.

The Zarqawi group statement said the recruits were heading off on holiday in the south of Iraq when they were ambush.

"Some children of the "The Al-Qaeda Group of Jihad in the Country of Two Rivers (Iraq)" have succeeded in killing 48 corrupt heads, members of ... the Iraqi guard," said the statement, published on the Islamist website (wwww.ansarnet.ws/vb).

It was not possible to verify the authenticity of the statement.

The Zarqawi group, formerly known as Al-Tawhid wal Jihad (Unity and Holy War) announced its name change on another Islamist website at the weekend, apparently to show its allegiance to the Al-Qaeda network of Osama bin Laden.

It was also not possible to verify the origin of that statement.

The lifeless bodies of the cadets were laid out in rows on the ground of a national guard base in Mandali and some of them were badly burnt.

Anger mixed with grief on the faces of the national guardsmen at the base. "This is a massacre, this is terrorism!" screamed one of them, who did not wish to be identified.

A man in a grey disdash (traditional male robe) sobbed and hit his head in anguish as two of his companions carried out the body of his brother from the row of victims and put it in a wooden coffin.

Earlier the police chief for Diyala province said the corpses were discovered on the road between Baladruz and Badra, south of Baquba, a town lying 60 kilometres (40 miles) northeast of the Iraqi capital in an area that is a hotbed of anti-US and anti-government sentiment.

The victims had been returning home to the southern Shiite-dominated cities of Amara and Kut after a 20-day training course at a desert camp near the Iranian border, said local council member Khadija Mohammed.

"The bodies were evacuated to a national guard base at Mandalikilometres east of Baquba)," she added.

The US-led military in Iraq has invested much time and money into training Iraq's army, police and national guard, with the ultimate aim of handing back contol of security to them and withdrawing from the country.

"I deeply regret the senseless loss of life, as I do all the other lives lost in this struggle, be they Iraqi or coalition," said Deputy for Coalition Military Training Brigadier Nigel Aylywin-Foster.

Asked about its potential impact on morale, however, the British brigadier said: "After the initial shock it will merely serve to strengthen the Iraqi Armed Forces resolve to defeat the perpetrators."

The recruits were from the Kirkush training base on a windswept desert plain near Mandalai on the country's eastern border with Iran.

The slaughter followed twin suicide car bombings against police and the Iraqi national guard on Saturday that killed 20 people.

It also comes after a slew of attacks on the country's security forces aimed at crippling its ability to stand on its feet.

Members of Iraq's security forces are a favourite target in an insurgency that flared up in the aftermath of last year's US-led invasion and which US and Iraqi officials are desperate to crush.

Almost 70 police recruits were killed in one suicide car bomb attack in July in Baquba, the capital of Diyala province.

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