Abu Musab al-Zarqawi has reportedly called on militants to carry out more suicide attacks in Iraq as a wave of violence swept across Baghdad, killing 24 people.

The call to arms, made in a tape posted on the internet today, came 24 hours after the country formed its first democratically elected government.

It was not possible to verify whether the tape really was made by Mr al-Zarqawi, a wanted terrorist who claims to lead al-Qaeda in Iraq.

In the latest wave of violence four car bombs went off almost simultaneously in Baghdad at 8am local time (0400 GMT), killing seven soldiers, two policemen and four civilians, and wounding a further 50 people. The car bombs were accompanied by a blizzard of mortar attacks which caused further injuries.

An hour later militants struck again in the capital, with a double car bombing. The tactic of waiting for police to gather at the scene of a car bomb before detonating another vehicle, to maximise the number of victims, has become a common ploy of insurgents.

Two hours later three more car bombs went off in the largely Sunni town of Madain, killing four policemen, three soldiers and two civilians. One car exploded outside the town's hospital, while another rammed a police vehicle.

Madain has been the scene of persistent kidnappings and murders by Sunni militants, directed against Shia Muslim families, culminating in an alleged mass kidnapping last week. Tens of mutilated bodies have since been found in the river Tigris nearby.

The recording allegedly made by Mr al-Zarqawi vows not to let the President Bush enjoy "peace of mind" and boasts that after two years the invasion of Iraq the insurgency is still going strong.

Mr al-Zarqawi has been convicted of terrorist offences in his home country of Jordan, and has claimed responsibility for most of the high profile militant attacks in Iraq in recent months.

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