Three senior members of the Islamic State of Iraq and al-Sham (ISIS) - including an aide to its leader - were killed in a U.S. airstrike in Iraq, a senior Iraqi security official told NBC News Thursday. The strike on the ISIS stronghold of Mosul killed Abu Hajar Al-Sufi, an aide to Abu Bakr al-Baghdadi, as well as an explosives operative and the military leader of nearby Tel Afar, the source said on condition of anonymity. Al Arabiya cited the Iraqi Defense Ministry saying Baghdadi's aide had been killed.

Pentagon Spokesman Col. Steve Warren could not confirm the deaths and said ISIS leaders had not been targeted. But he added that if ISIS leaders were embedded "inside troop formations they are likely to be killed." The U.S. has been carrying out airstrikes across the country's north after the brutal terror group gained ground in a murderous sweep in June. The U.S. and the West have stepped up their rhetoric against the group after what Obama's opponents said was a slow start in articulating a solution to the crisis.

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- Alexander Smith