A car bomber and a suicide bomber have struck a busy area in Baghdad's commercial district, killing at least nine people and wounding 19, officials say.

Ambulances arrived at the scene of Thursday's blast, which was quickly sealed off by security forces. A military helicopter hovered overhead and shop owners cleaned shattered glass from their stores.

"The first attack was a suicide car bomb between the court and a police base," Brigadier-General Saad Maan, Baghdad security spokesman, said on Thursday.

"After a few minutes, another suicide bomber ... blew himself up", he was quoted by AFP news agency as saying. 

The first explosion was from an explosives-laden car left in a parking lot in the Karrada neighbourhood, a police officer said.

The area is a busy commercial district where some government offices are also located, including courts and a hospital.

A few minutes later, a suicide bomber with an explosives belt blew himself up at the main gate of an office affiliated with the Higher Education Ministry, killing two policemen and one civilian, the police officer also said.

Six other people were wounded in that blast.

A medical official confirmed the causality figures, according to AP news agency. Both officials spoke on condition of anonymity because they were not authorised to talk to media.

Since last year, Iraq has been seeing the worst level of violence since sectarian violence in 2008.

The UN has said 8,868 people were killed in 2013, and more than 1,400 people were killed in January and February of this year.

No one immediately claimed responsibility for the attack on Thursday, which came two days after a series of car bombings rocked the capital and killed at least 34 people.

It was the bloodiest day in Iraq since April 28, when attacks claimed by the Islamic State of Iraq and the Levant on polling stations and other targets killed 46.

The latest attacks come also nearly two weeks after Iraqis cast ballots in the country's first parliamentary election since the US military withdrawal in 2011.

No preliminary results have yet been released.

Source: Agencies