BAGHDAD, Sept 22: Baghdad was engulfed in violence on Wednesday as 21 people were killed and more than 100 wounded in a car bomb attack and US-led offensives on Shia and Sunni rebel pockets in the capital.

An official from religious scholar Moqtada Sadr's movement said 15 people were killed and 52 wounded in an assault by the US military to reclaim parts of the Shia stronghold of Sadr City.

Naim al-Qaabi described the ongoing raids as "the most devastating operation in Sadr City" since the fall of Saddam Hussein's regime in April 2003. US Major-General Peter Chiarelli said in a statement that the operation was aimed at restoring stability in Baghdad by improving the living conditions of Iraqis.

"I think the key to improving the security situation in Baghdad is giving people hope through the execution of our large projects to fix the infrastructure," he said.

An AFP correspondent in Sadr City said gunfire and rocket-propelled grenade attacks were still ongoing at midday (0200pm PST). The impoverished district is littered with roadside bombs and has become a virtual no-go zone for US troops.

Meanwhile, a suicide car bomb targeting Iraqis queuing up to join the national guard ripped through a busy shopping area in the heart of Baghdad on Wednesday morning, police and witnesses told AFP on the scene.

"A suicide car bomb rammed into a group of people gathered to sign up for the Iraqi national guard" at a shopping complex on the central Al-Rabih Street, a police officer said.

"The suicide bomber drove onto the sidewalk and detonated his charge. Medical sources at the Yarmuk hospital said at least six people were killed and 54 wounded in the latest attack, which took place just a few metres away from the site where another car bomb was defused on Tuesday.

US army Lt Charles Heaton confirmed that Wednesday's attack was a suicide car bomb. A dozen vehicles in the vicinity of the blast were turned into charred shells and several shop fronts destroyed, and panicked residents ran through the debris and smoke to rescue the wounded.

An AFP reporter saw people burying body parts on the median strip which cuts the wide boulevard in two. Fresh fighting in the Sunni stronghold of Haifa Street in Baghdad erupted overnight, but there were no immediate reports of any casualties.

Sporadic but heavy gunfire was heard in the central neighbourhood, which is a mixture of posh high-rises and impoverished alleyways harbouring a loose alliance of Saddam Hussein loyalists and insurgents.

Violence in the capital was compounded by more bloodshed elsewhere in the country. The police chief of the northern town of Tall Afar, where US and Iraqi forces have recently conducted raids to crack down on Iraqi and foreign insurgents, was wounded in an assassination attempt, police said.

"Unknown attackers opened fire overnight on Colonel Ismail Ahmed Ismail's car," a police spokesman said, adding that one of his bodyguards was killed in the attack. An Iraqi civilian was also killed and two wounded when a roadside bomb went off early Wednesday near the town of Tikrit north of Baghdad, police said. -AFP