MOSUL, Iraq Gunmen rampaged through a Sunni district of the northwestern Iraqi town of Tal Afar overnight, killing about 50 people in reprisal for bombings in a Shi'ite area, Iraqi officials said on Wednesday.
Prime Minister Nuri al-Maliki, a Shi'ite, ordered an inquiry into reports the gunmen included policemen from his Shi'ite- dominated security forces, an official in his office said.
The attack was on the Sunni district of al-Wihda in Tal Afar, where tensions have been rising between Shi'ite and Sunni Muslim residents, mostly Turkish-speaking ethnic Turkmen.
The tit-for-tat violence in a town held up by President Bush only a year ago as an example of progress toward peace in Iraq, graphically illustrates the challenge facing Maliki in bridging an ever-widening sectarian divide.
There has been a sharp upsurge in violence in recent days outside Baghdad, epicenter of the communal bloodshed, where thousands of U.S. and Iraqi security forces are focusing their efforts to halt a slide to full-scale civil war.
"Shi'ite armed groups killed Sunni men inside their homes. More than 50 were killed," said Brigadier Najim al-Jubouri, mayor of Tal Afar, which is close to the Syrian border and the regional capital of Mosul.
He said 18 people had been detained. A security source who declined to be named said many of the suspects were policemen. A curfew was imposed as the Iraqi army took control of the city.
"I wish you can come and see all the bodies. They are lying in the grounds. We don't have enough space in the hospital. All of the victims were shot in the head," a doctor told Reuters by telephone from the main hospital in Tal Afar.
"Between 50 and 55 people were killed. I've never seen such a thing in my life," said the doctor, who refused to be named because he said he feared for his life.
Another source at the hospital put the death toll at 45, while police said 50 were killed. Major-General Khorshid Saleem, the head of the Third Army Division in Tal Afar, said the death toll was 70, with 30 wounded and 40 kidnapped.
"Militias conducted these acts, and if it had not been for the army interference the people killed in the carnage would be in the thousands," he told Reuters.
Gunmen raided the Tal Afar neighborhood shortly after twin truck bombings on Tuesday that police said killed 55 people and wounded 180. One suicide bomber lured victims to buy wheat loaded on his truck in a Shi'ite neighborhood. A second truck bomb exploded in a used car lot in a religiously mixed area.
An Iraqi army officer in Tal Afar said Iraqi troops had sealed off police stations in the town to try to bring the violence under control and arrested 20 policemen in connection with the shootings.
In March 2006, Bush called Tal Afar a "free city that gives reason for hope in a free Iraq" after U.S.-led forces freed it from al Qaeda in an offensive.
A year on, however, the city is beset by the same sectarian tensions between minority Sunnis and majority Shi'ites that have killed tens of thousands in Iraq since the bombing of a revered Shi'ite shrine in the town of Samarra in February 2006.
Violence has seen Shi'ites and Sunnis flee previously mixed neighborhoods, which are now largely segregated along sectarian lines. Some Sunnis in Tal Afar have complained that the arrival of Shi'ite-dominated security forces has led to oppression.
In other violence, Iraqi security forces opened fire and blew up two suicide attackers driving chlorine truck bombs outside a local government building in Falluja, in western Iraq, the U.S. military said.
Fifteen Iraqi and U.S. troops were wounded in the blasts and "numerous" Iraqi personnel sickened by the chlorine gas.
Insurgents have increasingly begun using chlorine bombs in a stepped-up campaign using unconventional weapons, although these have caused relatively few deaths.
U.S. and Iraqi troops also killed 25 suspected militants in operations in the Diyala River Valley north of Baghdad, which the U.S. military described as a base for the al Qaeda-led Islamic State in Iraq group.
(Additional reporting by Claudia Parsons, Aseel Kami and Mussab Al-Khairalla in Baghdad)