The violence began early Wednesday morning, when a bomb packed into a truck exploded next to a concrete barrier outside the Australian embassy in Baghdad.

Two Iraqis were killed and two Australian soldiers injured in the attack.

The al-Qaeda group in Iraq, led by the Jordanian-born terrorist Abu Musab al- Zarqawi, claimed responsibility for the bombing in a statement posted on the internet.

Over the next few hours a series of bombs went off throughout the city, firstly targeting a police headquarters, killing six policemen.

It’s thought insurgents blew up a house the police were raiding, flattening neighbouring homes.

A third bomber struck at the main gate to an Iraqi military garrison located at a disused airport in central Baghdad, killing three soldiers.

The US military reported a car bomb detonated southwest of Baghdad International Airport, killing two Iraqi security guards.

Hours later, one person died after another car bomb went off in northern Baghdad near a bank and a Shi’ite Muslim mosque.

Elsewhere in the capital, insurgents in a car fired on a Baghdad office of the Patriotic Union of Kurdistan, killing one of its members and wounding another.

Outside of Baghdad, an Iraqi police officer was killed in another car bombing in the largely Shi’ite city of Hillah south of Baghdad.

And fresh clashes erupted on Wednesday between US troops and insurgents in the northern city of Mosul.

A car bomb exploded beside a US convoy in the eastern part of Iraq’s third biggest city, and two Iraqis were killed when American troops opened fire after the blast, witnesses said.

There were no reported casualties among the Americans.

American and Iraqi officials have predicted a steady increase in violence in the run-up to the election, in which Iraqi voters will choose a National Assembly and provincial legislatures.

Sunni Muslim insurgents have vowed to disrupt the ballot.

The attacks, freshly endorsed by Osama bin Laden, remain a potent force despite US offensives intended to protect next month’s Iraqi elections.

Carlos Valenzuela, the chief UN election adviser in Iraq, said the intimidation of electoral workers by guerrillas seeking to derail this month’s balloting is “high and very serious.”

But he told reporters only a sustained onslaught by insurgents or the mass resignation of electoral workers would prevent this month’s national elections from going ahead.

Meanwhile a Sunni Muslim militant group has posted a video on its website showing the killing of two Iraqis who were working for a US company.