BAGHDAD, Aug 1: Thunderous car bombings echoed around Baghdad on Wednesday, killing at least 70 people, as Iraq's national unity coalition collapsed under the weight of sectarian tensions.

New government figures also revealed civilian deaths in the country rose by one third last month, dealing a further blow to a five-month-old security plan designed to stabilise Baghdad and allow for reconciliation.

Three large bombs tore through crowded districts of the capital, leaving at least 70 people dead and feeding the communal bitterness that has undermined Prime Minister Nuri al-Maliki's US-backed government.

In the largest blast, a truck bomb detonated near a filling station in the west of the city, setting fire to a huge fuel tank, killing at least 50 people and wounding at least 60 more, Iraqi security officials said.

A medic at the nearby Yarmuk Hospital said the emergency room struggled to cope with the wave of incoming wounded.

“There were not many lightly injured people, everyone had medium or severe burns. Some of them got beds, but others had to lie on the floor and some were given first aid then sent on to other hospitals,” he said.

Earlier a car bomb ripped through a busy shopping district, killing at least 16 Iraqis and wounding 14, according to Brigadier General Qassim Atta, an Iraqi army spokesman for Baghdad.

There was no word on who might have planted the bomb, but the area is known as a stronghold of supporters of Shiite leader Abdel Aziz al-Hakim, and previous attacks of this kind have been blamed on Sunni extremists.

A third car bomb in the southern neighbourhood of Dura, one of Baghdad's most notorious districts, killed three more people and wounded another five, according to security officials.

Three Iraqi policemen were also killed in a roadside bomb attack and an ambush by gunmen on a private car, a security official said.

As explosions rumbled across the city, ministers from the Concord Front, Iraq's largest Sunni bloc, resigned from the ruling coalition and effectively ended its claim to be a government of national unity.

“The Front announces its withdrawal from the government of Nuri al-Maliki and the deputy prime minister and the ministers will submit their resignation today,” said Rafie al-Issawi, minister of state for foreign affairs.

Sunni Vice President Tareq al-Hashemi will keep his job and the bloc's 44 parliamentarians will return to the National Assembly in September after its summer recess, when they will swell the growing ranks of the opposition.

The Front has accused the government of failing to rein in Shiite militias and of the arbitrary arrest and detention of Sunnis, but leaders seemed to leave the door open for future discussions.

“Our central and historic goal is reform. We will reconsider the withdrawal tomorrow if they review our demands,” Hashemi said.

Maliki's government is currently under intense pressure to make use of the space afforded by a five-month-old “surge” of US troops to hammer out political agreements between the rival factions.

In a video-conference call with US President George W. Bush, the weakened prime minister stressed dialogue with the Concord Front would continue and that his shrinking coalition would make every effort in the name of national unity.

“Dialogue with the brothers in the Concord Front will not stop despite their announcement of withdrawal from the government,” his office quoted him as telling Bush.

“The coalition will make every effort to consider positively all suggestions that serve the higher interests of the people and improve national unity.” But with parliament now on holiday without passing any of the benchmark reforms demanded by Washington, it is unlikely any progress will be made ahead of September's progress report to the US Congress on the surge.

In a further blow to the surge, numbers released by government ministries on Wednesday revealed that the number of civilians killed in Iraq's civil conflict in July rose to at least 1,652, 33 per cent more than in June.

The US military also said four more troops were killed on Tuesday, bringing US losses since the March 2003 invasion to 3,653, with 83 killed in July, according to an AFP count based on Pentagon figures.

In London, Britain confirmed that another of its soldiers had been killed in the southern city of Basra on Tuesday, bringing to 164 the number to have died in Iraq.—AFP