TAL AFAR, IRAQ - A series of bombings in this small but strategic northwestern Iraqi city is stoking fears of a return to sectarian conflict and raising questions about a strategy of handing urban security to Iraqi police.

Since April, at least four major bombings have killed about 40 people and wounded nearly 150 in Tal Afar, a city on the main route from Mosul to the east and the Syrian border 60 miles to the west. The deadliest was Aug. 8, when a suicide bomber detonated a truck packed with explosives in a vegetable market, killing at least 20 people, police said. U.S. officials blamed the attack on al-Qaida in Iraq.

The city's mayor, Najim Abdullah, fears that the removal of U.S. troops from his city and the deployment of Iraqi army soldiers to nearby Mosul have left his overwhelmingly Turkoman community vulnerable.

Those concerns have emerged even as insurgent attacks and sectarian bloodshed have ebbed over the past year throughout Iraq, and as the U.S. is considering a further reduction in the 145,000-member U.S. force following the July departure of the last of the troops sent in 2007 to curb sectarian violence.

Local officials fear extremists are taking advantage of the drawdown to strike back. And the officials lack confidence in the mostly Shiite Iraqi police.

"We used to depend mostly on coalition forces, but unfortunately the footprint of the U.S. has been reduced," Abdullah said, holding court outside his office in an Ottoman-era castle.

Control of Tal Afar, an agricultural city of about 220,000, with brown mud-brick houses resting on a saddle between two low mountains, is critical to securing northern Iraq, where al-Qaida in Iraq and other Sunni extremist groups remain active.

Violence swept the town in 2004 and 2005, sending most of its residents fleeing to nearby villages.

In September 2005, however, 5,000 Iraqi troops backed by a 3,500-strong U.S. armored force drove insurgents from Tal Afar. President Bush cited the operation as an example that gave him "confidence in our strategy."

But the recent bombings have taken place at a time when U.S. commanders have cut the number of U.S. troops patrolling Tal Afar down to a platoon, usually about 30 people. U.S. soldiers no longer man combat outposts in the city.

U.S. strategy calls for removing U.S. and Iraqi soldiers from Iraq's cities once they have been secured and replacing them with Iraqi police, long considered the weakest of the security services.

Iraq's government moved out a battalion of its troops to secure Mosul, where Iraqi forces launched an operation last May to wrest control from al-Qaida in Iraq.

The Tal Afar mayor complained that the government transferred experienced officers to Mosul without consulting civilian authorities. Their replacements were unfamiliar with the city, he said.

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