A rapid series of attacks spread over a wide area of Iraq have killed at least 55 people, targeting mostly security forces in what appeared to be another strike by al Qaida militants.

The apparently co-ordinated bombings and shootings unfolded over a number of hours in the capital Baghdad - where most of the deaths occurred - and 11 other cities.

They struck government offices, restaurants and one in the town of Musayyib hit close to a primary school. At least 225 people were wounded.

It was the latest in a series of large-scale attacks that insurgents have launched every few weeks since the last US troops left Iraq in mid-December at the end of a nearly nine-year war.

The Interior Ministry blamed al Qaida insurgents for the violence.

"These attacks are part of frantic attempts by the terrorist groups to show that the security situation in Iraq will not ever be stable," the ministry said in a statement. "These attacks are part of al Qaida efforts to deliver a message to its supporters that al Qaida is still operating inside Iraq, and it has the ability to launch strikes inside the capital or other cities and towns."

No group immediately claimed responsibility for the latest attacks, but targeting security officials is a hallmark of al Qaida.

The ongoing nature of the violence and the fact that insurgents are able to launch a variety of attacks over a wide territory in Iraq shows the country is still deeply unstable, despite government assurances it could protect itself when American troops left in December.

A senior Iraqi defence intelligence official said the attacks appeared to have been planned for at least one month. He predicted they aimed to frighten diplomats from attending the Arab League's annual summit that is scheduled to be held in Baghdad in late March.

Nationwide, security forces appeared to have been targeted in at least 14 separate attacks, including a drive-by shooting in Baghdad that killed six policemen at a checkpoint before dawn.