The stepped-up violence in the capital came as al-Qaeda leader Osama bin Laden, in an Internet audiotape attributed to him, warned of retaliation against Iraqi Shias, who he said have been waging a campaign of "genocide" against Sunnis.

It also coincided with a visit by Prime Minister Nuri al-Maliki, a Shia, to neighbouring Sunni Arab-dominated Saudi Arabia to garner its support for his national reconciliation plan.

Three car bombs went off in Baghdad's central Karradah district killing at least three people and wounding 16 according to a preliminary toll provided by a security official.

One of the explosions was directed against a police patrol in the area's busy Arasat street killing a policeman and wounding three civilians.

In nearby Hurriyah square in the Jadriyah neighbourhood a roadside bomb exploded in the path of a convoy carrying Iyad Jamaleddin, a turbaned Shia MP with the Iraqi National List parliamentary bloc of former premier Iyad Allawi.

That attack wounded three passersby said a security official.

Jamaleddin had called recently for reconciliation with members of the former ruling Baath party of ousted leader Saddam Hussein, a position strongly opposed by hardline Shias in parliament and Maliki's government.

The attempt on his life came a day after Taiseer Najeh Awad al-Mashhadani, an MP from the National Concord Front, the largest Sunni Arab bloc in parliament, was seized in Baghdad along with eight of her bodyguards.