A suicide bomber on Monday killed seven people and wounded an MP in an attack at an entrance to Baghdad's heavily secured Green Zone, where the Iraqi government is based, officials said.

The attacker drove up to the entrance situated at the July 14 bridge, which is manned by Iraqi soldiers and lies across the Tigris River from the Green Zone, before detonating an explosives-rigged vehicle, an interior ministry official said.

The blast killed seven people and wounded at least 24, according to the official and a medical source. MP Habib Hamza al-Turfi was among those wounded, another deputy, Ammar Toma, told AFP.

The mangled remains of a Humvee armoured vehicle could be seen at the site of the blast, which was swarming with Iraqi soldiers. Twisted and burned pieces of metal were scattered around for dozens of metres (yards).

Iraqi soldiers and police armed with M-16 and Kalashnikov assault rifles cordoned off the main road leading to the July 14 entrance, and deployed Humvees mounted with machine guns on the street.

Federal police and soldiers also stopped cars and pedestrians from approaching the main road via side streets, though some people still gathered to look on.

The Green Zone, where the United States and British embassies are also situated, is among the most heavily fortified areas in Iraq, surrounded by heavy concrete blast walls and guarded by Iraqi soldiers armed with equipment ranging from assault rifles to US-made Abrams tanks.

While violence in Iraq is down from its peak in 2006 and 2007, attacks are near-daily occurrences, killing hundreds of people per month and wounding many more.

Insurgents have shown they can strike at even the most highly-secured sites in the country, with targets in recent months including a military base, the anti-terrorism directorate in Baghdad, and a prison.

In late November, a suicide bomber detonated an explosives-laden vehicle near Iraq's parliament, inside the Green Zone.

Police and army checkpoints are set up around Baghdad, but the security forces that man them often employ "bomb detectors" from British firm ATSC that have been proven to be worthless at detecting weapons or explosives.

And any searches of vehicles are usually cursory and limited to a request to look in the trunk of the car.