BAGHDAD, Iraq - The British army in Basra said it arrested two prominent members of a militia affiliated with outspoken Shiite cleric Muqtada al-Sadr, whose armed followers quickly took to the streets of the southern city to demand their release.

Sheik Ahmed Majid Farttusi and Sayyid Sajjad were detained in an early morning raid and are accused of being involved in attacks that killed at least nine soldiers, according to a statement from coalition forces.

The statement described the two as leaders of al-Sadr's Mahdi Army, which clashed with U.S. forces in Baghdad and the southern city of Najaf last year. Another man was also arrested in yesterday's raid, but was not named.

"I am well aware that the people that we have arrested are prominent individuals in Basra," said Brig. John Lorrimer, commander of the British Army's 12th Mechanized Brigade. "But let me make it absolutely clear: We have acted against them as individuals, not as members of any particular organization."

Also yesterday, Iraqi officials announced that National Assembly member Faris Nasir Hussein, a Kurd, was killed by gunmen late Saturday, along with his brother and his driver.

He is the third member of Iraq's parliament to be assassinated since members took office earlier this year. Another assembly member, Haider Qasim, was wounded in the incident.

The men were traveling to a meeting held yesterday in Baghdad in which the assembly gave final approval to the country's draft constitution and submitted it to the United Nations, which plans to print about 5 million copies in advance of a nationwide referendum to be held by Oct. 15.

After the arrests in Basra yesterday, dozens of Mahdi Army members wielding AK-47s marched in protest to the provincial governor's office. They withdrew by early afternoon following a meeting with the governor.

Al-Sadr's Mahdi Army had remained largely out of the spotlight since last year's uprising against U.S. forces, as the cleric publicly eschewed armed confrontation in favor of the political process, while maintaining his anti-American rhetoric.

But after demonstrators burned Sadr's office in Najaf last month, Mahdi Army members occupied large parts of several southern cities, including Basra, and launched attacks against the offices of a rival Shiite militia, the Badr organization.

A young, brash cleric and the son of an assassinated ayatollah who was among the country's most revered religious leaders, al-Sadr and his followers have been vocal opponents of the U.S. presence in Iraq since the end of the 2003 invasion.

The initial version of the military's statement sent to reporters referred to the Mahdi Army as a "terror organization." A corrected version sent about an hour later removed that reference.

"We condemn the arrest of the Shaikh Fartusi and Sayyid Sajjad as they have not been active, especially after the closure of the Sadr office in Basra six months ago,"said Sayyid Mustafa Yaqubi, a senior member of al-Sadr's organization who himself was recently released from U.S. custody. "If they consider the Mahdi army terrorists, I dare them to bring any evidence that it is a terrorist army."

Fartusi was reportedly held for two days by U.S. forces in April 2003, touching off demonstrations in Baghdad.

Elsewhere in Iraq yesterday, in the northwestern city of Tall Afar, where U.S. and Iraqi forces continued to wrap-up an offensive that began early this month, six insurgents were killed by American soldiers raiding a pair of "safe houses," the military said in a statement.

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