Suicide bomber kills senior Iraqi army officer

No one claimed responsibility for the attack. But suicide bombings are the hallmark of al Qaeda's local wing, Islamic State of Iraq, which aims to take back ground lost in its long battle with U.S. and Iraqi forces.

Sunni Islamist insurgents tied to al Qaeda have stepped up bombings on Iraqi Shi'ite targets and security forces in a campaign of sectarian violence a year after the last U.S. troops left the OPEC country.

One bomber was shot outside the home of Brigadier-General Awni Ali, the director of the Defence Ministry's intelligence school, in the northern town of Tal Afar. But a second attacker managed to detonate his explosives.

"Guards killed one suicide bomber, but when the brigadier general and his bodyguards went out another bomber ran among them and blew himself up," a local official said.

Tal Afar is near the Syrian border, about 420 km (260 miles) north of Baghdad and just west of the volatile northern city of Mosul. The town has a large Shi'ite Muslim population in a volatile province that is home to many Sunni Arabs as well as Christians, ethnic Kurds and Turkmen.

Increasing sectarian violence has accompanied growing political unrest in Iraq as thousands of Sunni Muslims in western provinces rally against Shi'ite Prime Minister Nuri al-Maliki, accusing him of marginalizing their minority sect.

More than 10 suicide attackers have struck security forces, Shi'ite targets and a lawmaker since January.

Violence is far from the sectarian bloodletting that killed tens of thousands in 2006-2007. But after the last U.S. troops left in December 2011, insurgents have carried out at least one big attack a month.

Last year, more than 4,400 people were killed, the first annual climb in Iraq's death toll in three years.

Sunni unrest and renewed violence are worsening fears the war in neighboring Syria - where Sunni rebels are battling President Bashar al-Assad, an ally of Shi'ite Iran - could undermine Iraq's delicate sectarian and ethnic balance.

Islamic State of Iraq, though weakened after years of war with U.S. troops, has benefited from the inflow of Sunni Islamists and arms into Syria. Security officials say insurgents want to regroup in Iraq's western desert near the Syrian border.

(Writing by Patrick Markey; Editing by Angus MacSwan)