The Iraqi Prime Minister has made a desperate plea for a halt to the sectarian conflict gripping his country, as the death toll rose to nearly 400 in four days following a multitude of deadly bomb and shooting attacks.

Nouri al-Maliki called for a "consolidated front" of differing religious denominations within his country to help curb the spiralling violence, in an impassioned plea.

However only hours after he spoke, a further 122 people were killed in a series of marketplace bombings in Shia areas of Baghdad and the town of Khalis, to the north of the capital, late last night.

Of the total, at least 82 were slaughtered in a double suicide bombing at a popular Baghdad market, while 40 died in three coordinated blasts at Khalis.

In his statement calling for an urgent end to the violence, Mr al-Maliki said: "We call on you (Iraqis) not to allow the evil ones to triumph and to cooperate with your armed forces.

"We pledge to you that we are determined to pursue the criminals and those who support them with words or actions. Justice will reach them sooner or later."

He added: "The country is facing many challenges which need a consolidated front, in which all Iraqis must participate."

This morning, American forces claimed to have scored a victory in their battle against the insurgency by reportedly masterminding the arrest of a suspect linked to a number of sophisticated roadside bombs.

The militant, who was detained jointly by US and Iraqi forces in an early morning raid at a Shia district of Baghdad, was believed to be tied to networks bringing the weapons known as Explosively Formed Projectiles, or EFPs, into Iraq, the American military said.

However, news of the coup was overshadowed by reports that another US soldier had been killed in a roadside bomb attack in the capital, bringing the American military's losses in Iraq since the March 2003 invasion to 3,243, according to the Pentagon.

In a further blow, a statement made today by Moqtada al-Sadr, the radical Shia cleric, blamed the US for his country's growing problems and called for a mass demonstration to mark April 9, the fourth anniversary of Baghdad's fall.

The statement was the first by Mr al-Sadr since March 14 when he called on his supporters to resist US forces in Iraq through peaceful means.

The US believes that Mr Al-Sadr is in Iran. However, his aides insist that he is still in Iraq and claim he made his latest statement to worshippers during Friday prayers at a mosque in Kufa, a holy Shia city south of Baghdad, which they say Mr al-Sadr frequently addresses.

"I renew my call for the occupier (the United States) to leave our land," he said in the statement, according to the AP news agency.

"The departure of the occupier will mean stability for Iraq, victory for Islam and peace and defeat for terrorism and infidels."

Mr Al-Sadr, whose Mahdi Army militiamen fought US troops in 2004 but have generally cooperated with the ongoing US-Iraqi security push in Baghdad, blamed the presence of US forces in Iraq for the violence raging in the country.

"You, oppressed people of Iraq, let the entire world hear your voice that you reject occupation, destruction and terrorism," he said in calling for the April 9 demonstration.

The last few days have seen some of the worst violence, perpetrated by both Shia and Sunni extremists, that Iraq has seen since the US-British invasion.

In the most gruesome incidents, around 55 people died in two market-place suicide bombs at a Shia district in the town of Tal Afar on Tuesday.

Enraged Shia gunmen, many alleged to be policemen, then executed about 70 Sunni men in a shooting spree the next day, with their victims reportedly rounded up and shot in the back of the head.

The Iraqi Army said it detained 18 policemen for helping to carry out the atrocity, and drafted in replacement officers from the nearby town of Mosul.

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