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Karim Kadim, Associated Press
Iraqi security forces stand guard as Shiite pilgrims march towards Karbala for the Arbaeen holiday in Baghdad, Iraq, Tuesday, Dec. 9, 2014. Arbaeen marks the end of a forty day mourning period following the anniversary of the 7th century martyrdom of Imam Hussein, the Prophet Muhammad's grandson.

BAGHDAD — Iraqi officials say a bomb blast and mortar fire targeting Shiites have killed seven people in Baghdad.

The attacks came as U.S. Defense Secretary Chuck Hagel visited the Iraqi capital for a first-hand report on the battle against Islamic State militants.

Police officials say the bomb went off in western Baghdad's Baiyaa neighborhood on Tuesday afternoon, targeting Shiite pilgrims bound for the holy city of Karbala. The explosion killed four people and wounded 13.

After sundown, mortar shells struck in three separate Shiite areas in northern Baghdad suburbs, killing three people and wounding 12.

All officials spoke on condition of anonymity because they were not authorized to talk to media.

Nobody immediately claimed responsibility for the attacks, but Islamic militants frequently attack Shiites, whom they consider to be heretics.