At least 172 people, including women and children, were killed today in a spate of bombings in Baghdad, making it the single bloodiest day since US troops increased their numbers in the city.

By far the deadliest of four strikes was a suspected Sunni car-bomb close to a packed market in al-Sadriyah, near central Baghdad, which caused a massive fire that killed at least 122.

The area is inhabited by a mixed Kurdish and Shia population, and most of those killed were shopping in the market.

Among the dead were also reportedly several construction workers, who had been rebuilding the marketplace after a bomb destroyed many shops and killed 137 people there in February.

The number of fatalities from the incident was expected to rise further as 145 other people were reported to have been injured in the blast, according to the AP news agency.

Passers by at the market reported that the explosion caused a huge fire that tore through stalls and engulfed vehicles and people. A huge plume of putrid black smoke spiralled into the air.

Fire engines battled to put out the flames as dozens of ambulances and pick-up trucks ferried the wounded to hospital and civilian volunteers wrapped charred bodies in carpets for transport to the city’s overflowing morgues.

Angry Iraqis who lost loved ones lashed out at Iraqi Prime Minister Nouri al-Maliki, blaming his US-backed Government for failing to bring law and order to the streets of the capital, nearly a year after it took office.

"Down with Maliki! Where is the security plan? We are not protected by this plan," they shouted as an angry mob pelted Iraqi and American soldiers who scrambled to the scene with stones.

In other blasts during a horrific day in Baghdad a suicide car bomber crashed into an Iraqi police checkpoint at the entrance to Sadr City, the capital's biggest Shia neighbourhood and a stronghold of the radical anti-American cleric Muqtada al-Sadr, killing 33 and wounding 45.

A third explosion saw a parked car explode near a private hospital in the central Baghdad neighbourhood of Karradah, killing 11 people and wounding 13. The blast was reported to have damaged the Abdul-Majid hospital and other nearby buildings.

The other explosion, on a minibus in the north-western Risafi area killed four and wounded six others, officials told AP.

The death toll incurred in the wartorn country increased still further when it was later revealed that four policemen in Baghdad had been ambushed and killed when gunmen intercepted their patrol south of the city centre.

Foreign Secretary Margaret Beckett condemned the bombings, and claimed those who committed them were deliberately undermining democracy.

“This latest carnage in Baghdad is another appalling example of the lengths to which those who offer only death and destruction will go to in trying to undermine democracy in Iraq," Mrs Beckett said.

“My thoughts are with the families and friends of those killed and injured in these horrific attacks. Such acts only strengthen our determination to continue to support the people and government of Iraq and underline the importance of the reconciliation process.”

As the number of people confirmed dead rose, it became clear that the toll would be by far the biggest single number of fatalities since the US 'troop surge' brought greater numbers to Baghdad in February in a bid to wipe out the insurgency.

The number eclipsed the most serious day of violence before that, on March 30, when 122 were killed in a series of marketplace bombings in Shia areas of the city, during a week when a total of nearly 400 people of various ethnic denominations were killed all over Iraq.

On April 12, violence reached the heart of the Iraqi Government when a bomb at the country's Parliament building in Baghdad's heavily fortified 'green zone' killed one MP and injured more than 20 others.

The chaotic events in Baghdad contrasted, however, with those in the British-controlled areas of the south, where UK forces today handed over control of an unruly province to Iraqi control.

Described as Iraq's 'wild west' province, Maysan borders Iran and is believed to be a key smuggling zone for weapons coming from the east. Withdrawal from Maysan leaves the British Army in direct control only of Basra.

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