Iraqi interim Prime Minister Iyad Allawi said on Wednesday that at least 10 Iraqis, including three Iraqi national guards, have been confirmed killed and another 40 wounded when a suicide car bomber blew himself up just outside the Green Zone in central Baghdad, CNN reported.

Allawi, who had just visited the bomb site, vowed that his government will bring those responsible for the carnage to justice.

The blast took place at around 9:30 a.m. (0530 GMT) when a suicide bomber drove a car slowly to the entrance to the Green Zone and detonated it as many other vehicles queued to drop visitors to the heavily-fortified complex, CNN said.

The explosion caused "many, many more casualties" and the number could continue to rise, an Iraqi national guard told CNN on the blast scene.

Huge columns of black smoke were seen miles away, a witness said.

Thursday coincided with Iraq's July 14 holiday, which marks the bloody overthrow of the country's monarchy in 1958.

It was the first major car bombing in Baghdad since Allawi's government took over power from US-led occupation authorities on June 28.

The Green Zone, home to the US-led coalition authorities before the power transfer to Iraqis, is now called the International Zone that houses the US Embassy, as well the Iraqi interim government.

On May 17, suicide car bombers killed Izzedeen Salim, the then rotating president of Iraq's Governing Council as he entered the Green Zone.