A Sunni tribal leader instrumental in driving al Qaeda out of Iraq's Anbar province was killed by a bomb attack on Thursday, less than two weeks after he met US President George W Bush.

Abdul Sattar Abu Risha was killed near his home in Ramadi, capital of Anbar. He was the most influential leader of an alliance of Sunni Arab tribes that joined forces with US troops to push al Qaeda from much of the western region.

Two bodyguards and Abu Risha's private secretary were also killed in the attack on the day Iraq's Sunni Muslims marked the start of the holy fasting month of Ramadan.

"The sheikh's car was totally destroyed by the explosion. Abu Risha was killed," Ramadi police officer Ahmed Mahmoud al-Alwani told Reuters.

Police sources said he was killed by a roadside bomb. But one bodyguard who was not with Abu Risha at the time said a bomb had been planted in his car.

"We believe Abu Risha was one of the most important security personnel in Iraq," said Brigadier-General Abdul-Kareem Khalaf, spokesman for the Interior Ministry.

"The minister of interior has made an order that a statue be erected where he was killed or in any other place that the people of Anbar select."

Abu Risha set up an alliance of tribal sheikhs in Anbar last year to fight Sunni Islamist al Qaeda, an effort which has been held up by US  leaders as one of the biggest success stories in improving security after more than four years of conflict.

During his unannounced visit to Anbar early last week, Bush said security gains in the vast desert region were an example of what could happen elsewhere in Iraq.

 From 2003 until last year, Anbar was the heartland of the Sunni Arab insurgency and the most dangerous part of Iraq.

Al Qaeda once controlled large swathes but the network angered local tribal leaders with its indiscriminate killing of civilians and harsh interpretation of Islam.

Abu Risha was instrumental in getting young men in Anbar to start joining local police forces, a development that has sharply reduced levels of violence and forced many al Qaeda fighters to flee to other provinces.

It was one of the first examples of the U.S. military working with tribal leaders in Iraq to develop local police to secure their own communities.

The US military commander in Iraq, General David Petraeus, highlighted the "particularly dramatic" security gains in Anbar during testimony to Congress in Washington this week.

After meeting Bush, Abu Risha told an Iraqi television station: "We told President Bush that we are Iraqis and that we do not believe in sectarianism at all. We want to be united and build Iraq together."

Despite the better security in Anbar, the tribal alliance had shown signs of splintering over dissatisfaction with Abu Risha's leadership and infighting between tribal leaders.

Bush is expected, in a televised address on Thursday, to endorse plans for limited cuts in U.S. troop levels in Iraq but will offer little else to sceptical Americans looking for a change of course in the unpopular conflict.-Reuters