Baghdad was today hit by a series of huge explosions, killing at least 86people and injuring hundreds more, as Iraq suffered its bloodiest violence since US troops withdrew from urban areas at the end of June.

The deadliest of the six blasts – which happened in quick succession – targeted the foreign ministry.

The truck bombing killed at least 59 people, a toll expected to rise as rescue workers remove rubble, and injured 250.

The 10-storey building, just outside the heavily fortified Green Zone, was severely damaged in the explosion. Concrete slabs were blown away, crushing nearby cars.

"The windows of the foreign ministry shattered, slaughtering the people inside," an employee at the ministry told Reuters. "I could see ministry workers, journalists and security guards among the dead."

The force of the explosion damaged nearby buildings, covering a large area in debris and broken glass.

Windows in the parliament building, inside the Green Zone, were blown out by the explosion.

The apparently coordinated attacks began with a car bombing near the finance ministry in northern Baghdad.

A later blast, also close to the ministry building, targeted a joint Iraqi police and army patrol, killing eight people and injuring 22.

Another explosion in the commercial area of the Baiyaa district, in the west of the capital, killed two people and wounded 16.

Officials said a bombing in the commercial district of Bab al-Muadham killed six people and injured 24.

The attacks demonstrate that insurgents maintain the capacity to carry out spectacular bombings at will.

A recent rise in the number of explosions has hit efforts to restore a semblance of normality to Baghdad.

In recent months, Iraqi security forces have begun removing concrete blast walls, which have been credited with helping reducing violence.

US troops withdrew from Iraq's cities on 30 June under a security pact that outlines a full US withdrawal by the end of 2011.

The US president, Barack Obama, has ordered all combat troops out of Iraq by the end of next August, leaving up to 50,000 soldiers in training and advisory roles.

Today's attacks came six years to the day after the first large insurgent bombing following the 2003 invasion of Iraq destroyed a UN building in the north of Baghdad, killing the Brazilian envoy, Sérgio Vieira de Mello, and 13 others.

In the years since, thousands of people across the country have died in explosions.

The level of violence had subsided over the past 18 months, but the relative calm has been disturbed by recent attacks.