The bombardment targeted the terrorist organisation's gatherings in the area of Khazar, located between the rebel-held city of Mosul and the Kurdish city of Erbil, the official added on condition of anonymity.
The strikes are the latest since US President Barack Obama authorised on Thursday the attacks against the al-Qaeda splinter group, which has seized large swathes of Iraq.
Obama said the strikes, which started on Friday, could prevent a possible "act of genocide" against displaced minority communities, including thousands of Yazidis trapped on Sinjar Mountain without food or water.
US Deputy National Security Adviser Ben Rhodes met on Friday at the White House with Yazidis to discuss their community's dire humanitarian situation in northern Iraq where jihadists have consolidated a foothold.
The participants shared their personal stories about the suffering their families are facing at the hands of the Islamic State, said deputy National Security Council spokeswoman Bernadette Meehan.
The militants' sweeping advances in Iraq since early June have sent many thousands of minorities fleeing from their homes.
In late June, Islamic State leader Abu Bakr al-Baghdadi declared himself to be caliph, and announced the establishment of an Islamist caliphate in the territory under the jihadist group's control in Iraq and Syria.