A security source said bodies had been arriving at the hospital in the city of Baquba in Diyala province on Friday, Al Jazeera reported.
Such attack could hurt efforts by Iraq's new prime minister, Haider al-Abadi, to form a government that can unite Iraqis against the so-called Islamic State in Iraq and the Levant (ISIL), the group that has seized large parts of the country.
Attacks on mosques have in the past unleashed a deadly series of revenge killings and counter attacks in Iraq, where violence has returned to the levels of 2006-2007, the peak of a sectarian civil war.