(Recasts with November civilian death toll)

By Waleed Ibrahim and Alaa Shahine

BAGHDAD, Nov 30 (Reuters) - A crackdown on the entourage of a top Sunni Arab politician on Friday showed sectarian tension remains high in Iraq despite the number of civilians killed in violence falling dramatically this month.

Government figures showed 538 Iraqi civilians were killed in November, a fall of 29 percent from the previous month and the lowest figure since sectarian violence exploded after an attack on a Shi'ite shrine in February 2006.

The government's tally was running at nearly 2,000 civilian deaths per month before the United States launched a "surge" of 30,000 additional troops at the beginning of this year.

Apart from the impact of beefed-up U.S. troop numbers, military commanders credit the reduced violence on the growth of informal neighbourhood police units and a ceasefire by the Mehdi Army militia of anti-American cleric Moqtada al-Sadr.

But in a sign of bubbling tensions, Iraqi security forces arrested dozens of people including the son of the leader of the largest Sunni Arab political bloc in a pre-dawn raid after a car rigged with explosives was found near the politician's office.

The government said Adnan al-Dulaimi, whose Accordance Front is the Sunni Arab bloc with the most seats in parliament, could be stripped of the immunity from prosecution he holds as a parliament member if he is found to have links to car bombs.

"No one is above the law. Dr Adnan al-Dulaimi has immunity but this does not exempt him from questioning and accountability," government spokesman Ali al-Dabbagh said.

"The case is very serious and the accusations against him are very serious. He has to prove his innocence. He will be called for questioning. If the charges against him are proven, his immunity will definitely be lifted."

Dulaimi rejected the accusations.

"This is all not true. These are false accusations," Dulaimi told Reuters. "We are the ones who are subject to terrorism."

Seven people were arrested on Thursday at Dulaimi's office and 29, including Dulaimi's son Mekki, were seized in a raid early on Friday at Dulaimi's house, said Brigadier General Qassim Moussawi, security spokesman for Baghdad.

"We have also found quantities of weapons and uniforms of the army and police at the home of Dr. al-Dulaimi," he told Reuters. "Dulaimi's bodyguards are suspected of having links to car bombs and killings. There are confessions against them."

WRECKED CAR

Dulaimi's party put the number of detainees at 53. The U.S. military said the total was more than 40.

The wreckage of a four-wheel drive vehicle could be seen on the road outside a charity run by Dulaimi next door to his main offices in Baghdad, where security forces detonated the car after discovering it was rigged with explosives on Thursday.

Windows had been blown out of the charity building, which was covered with black smoke, and its main gate was destroyed.

Moussawi said the car bomb was found when security forces chased a suspected fugitive involved in a shooting into Dulaimi's compound.

The U.S. military said one of Dulaimi's guards had a key to the car that was rigged as a bomb. Two bystanders were hurt when one of the guards escaped, and five American soldiers and one bystander were hurt in the controlled blast when the car was destroyed, the U.S. military said in a statement.

Dulaimi had been asked to stay in his house "for his own personal safety," it said.

Dulaimi's bloc quit Prime Minister Nuri al-Maliki's Shi'ite-led government in August and has rejected efforts to lure it back. It wants a greater say in security policy.

The U.S. military has so far reported 37 of its soldiers killed in November, one fewer than last month. If the figure is not updated in the coming days, it will be the lowest figure since March 2006. (Writing by Peter Graff; editing by Robert Woodward)

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