BAGHDAD: Three blasts including two car bombs and a massive explosion in front of the Iranian embassy rocked Baghdad on Sunday, killing at least 15 people and wounding dozens, officials said.

The explosions occurred within minutes of each other, shattering windows in nearby buildings and sparking bursts of gunfire.

Large plumes of smoke billowed across the Iraqi capital as ambulances and emergency services rushed to the scene.

Two apparently co-ordinated car bombs hit the upscale west Baghdad neighbourhood of Mansur, with one striking close to the residence of the German ambassador, an interior ministry official said.

Shortly afterwards, at around 11:20 am (0920 GMT), an enormous explosion struck near Tehran's mission in the Salhiyeh neighbourhood of central Baghdad.

The interior ministry official said at least 15 people were killed and 25 wounded, while a medical official at Yarmuk hospital in west Baghdad said it had so far received nine dead, including two women, and 52 wounded.

Sunday's blasts follow major sets of co-ordinated explosions in the Iraqi capital in August, October, December and January which in all killed more than 400 people.

They came as Iraqi political parties negotiate to form a government, nearly a month after a general election that left four main blocs, none with sufficient seats to form a parliamentary majority on their own.

Iraq's two biggest political blocs -- the Iraqiya list of ex-premier Iyad Allawi and the State of Law Alliance of sitting Prime Minister Nuri al-Maliki -- are battling to form coalition governments, more than a week after results from the March 7 poll were released.

Security officials have warned that a protracted period of coalition building could give insurgents an opportunity to further destabilise Iraq.

Sunday's violence follows an attack blamed on Al-Qaeda at a village south of Baghdad in which security officials said 25 villagers were rounded up and shot execution-style early Saturday morning.

An Iraqi security spokesman said on Sunday that the gunmen who carried out the massacre posed as American soldiers in a bid to reassure villagers before shooting them.

"They wore American military uniforms, two or three of them spoke English, to give the impression that they were American forces," said Major General Qassim Atta, the spokesman for the Iraqi security forces' Baghdad operations.

Twenty-five men have been arrested in connection with the rampage in the village of Sufia on the southern outskirts of Baghdad that began just before midnight Friday and continued for at least two hours.

The victims were from Iraqi families linked to an anti-Qaeda militia.

Though the frequency of attacks has dropped significantly across Iraq since its peak in 2006 and 2007, figures released on Thursday showed the number of Iraqis killed in violence last month, 367, was the highest this year.

The death toll for March also represented the fourth consecutive month in which the overall number of people killed was higher than the same month a year previously.