Six car bombs exploded across Baghdad on Monday, killing at least 34 people and wounding scores, police said, after the arrests of Sunni Arab fighters raised tension in the Iraqi capital.

A blast at a popular market in the Shi’ite Muslim slum of Sadr City in east Baghdad killed at least 10 people and wounded 65. Another car bomb blew up next to a group of labourers queuing for work, killing six people and wounding 16.

Hours later, south Baghdad’s Um al-Maalif neighbourhood was shaken by two blasts in a market, killing 12 and wounding 25.

The latest attacks underscore the challenges Iraqi security forces face as U.S. combat troops prepare to withdraw by Aug. 31 2010, with all U.S. troops due to leave by the end of 2011.

Overall violence has fallen in Iraq to levels not seen since just after the 2003 U.S. invasion, but militants still carry out large-scale bombings, especially in the capital and the north.

Preventing all car bombs in the crowded streets of Baghdad — a sprawling maze of crumbling buildings and concrete walls, housing five million people — is all but impossible.

Two other blasts shook a market area of Husseiniya, on Baghdad’s northern outskirts, killing four, and a street in eastern Baghdad, apparently targeting the convoy of an Interior Ministry official, killing one of his guards and a bystander.

“The explosion caused major damage to buildings and they even hurt some children,” shopkeeper Abdul-Jabar Saad said of that attack, which he witnessed. “God damn these people.”

SUNNI GUARDS OR AL QAEDA?

The attacks followed a week of arrests in Baghdad by Iraq’s Shi’ite-led government of Sunni Arab fighters known as Awakening Councils, or Majalis al-Sahwa in Arabic.

The Iraqi government insists it is only detaining those wanted for grave crimes, but the fighters — many of them former insurgents — fear it is settling sectarian scores.

Analyst Kadhum al-Muqdadi, a Baghdad University professor, suggested the bombs might be a coordinated strike in response to the raids, one of which sparked clashes just over a week ago between Iraqi forces and supporters of an arrested Sahwa leader.

“Any security action carries the risk of a reaction,” he told Reuters. “These could be the work of Sahwas or just of opportunists exploiting this issue.”

The Sahwas first switched sides and joined with U.S. forces to battle Sunni Islamist al Qaeda in late 2006, manning checkpoints and conducting raids throughout the country.

Many have been killed in insurgent attacks.

The Iraqi government started taking control of them late last year, but mistrust runs deep. Some of the guards complain they have not been paid for two months, although Iraqi officials say that was an administrative glitch that has now been fixed.

Sheikh Hameed al-Hayyes, a founder of the Sahwa movement, said the bombings were unlikely to be the work of the guards.

“There were bombings in Baghdad before the arrests and after the arrests … these attacks were by al Qaeda,” he said.

Baghdad security spokesman Qassim al-Moussawi also said the attacks “carry the fingerprints of al-Qaeda-linked groups”.

Iraqi and U.S. officials say a small number of the 90,000-odd Sunni guards still have links to al Qaeda and other insurgents. But the government insists they are a minority.

“Al Qaeda is trying to infiltrate the Sahwa, but I think it will not succeed, because the Sahwa have seen their crimes and brutality,” said government spokesman Ali al-Dabbagh.

Bomb attacks continue on an almost daily basis in Iraq, despite the sharp fall in overall violence. The last big bomb attack in Baghdad killed 20 people in a shopping district on March 26.