(Adds details, clarifies spelling of mastermind's name)

BAGHDAD, Sept 9 (Reuters) - A U.S. air strike killed a senior al Qaeda militant who masterminded truck bombings on Iraq's minority Yazidi community last month that killed more than 400 people, the military said on Sunday.

"On September 3, a coalition air strike killed the terrorist responsible for the planning and conducting of the horrific attack against the Yazidis in northern Iraq on August 14," military spokesman Rear Admiral Mark Fox told a news conference.

Iraq's government has put the death toll at 411 from the suicide bombings, although the Iraqi Red Crescent has said it could be more than 500. The bombings in the villages of Kahtaniya and al-Jazeera were the deadliest militant attacks in Iraq since the U.S.-led invasion in 2003.

A U.S. military statement named the mastermind as Abu Mohammad al-Afri, adding he was the al Qaeda "emir", or prince, in the area where the bombings took place.

Fox said he was an associate of Abu Ayyab al-Masri, the Egyptian leader of al Qaeda in Iraq.

Afri was killed in an air strike southwest of the northern city of Mosul, Fox said.

"He is no longer a threat to the Iraqi people. We will continue to hunt down al Qaeda in Iraq and their operatives who conduct indiscriminate and brutal attacks against the Iraqi people," Fox said.

Scores of clay-built homes were levelled in the bombings, burying entire families in rubble.

The U.S. military has previously said Sunni Islamist al Qaeda was the prime suspect in the attacks.

Al Qaeda views Yazidis, who are members of a pre-Islamic Kurdish sect, as infidels.

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