Mosul residents said the Prophet Jirjis Mosque and Shrine was bombed and destroyed by the radical jihadist group. They spoke anonymously to The Associated Press for fear of reprisal.
The complex was built over the Quraysh cemetery in Mosul in the late 14th century, and included a small shrine dedicated to Nabi Jerjis, the Prophet George.
The al-Qaeda breakaway Islamic State group captured large swaths of land in western and northern Iraq, including Mosul, Iraq's second largest city, which was captured in June. The group has imposed a self-styled caliphate in territory they control in Iraq and Syria, imposing their harsh interpretation of Islamic law.
Among the mosques destroyed in Mosul last week were the Mosque of the Prophet Sheeth (Seth) and the Mosque of the Prophet Younis, or Jonah, said to be the burial place of the Prophet Jonah, who in stories from both the Bible and Quran is swallowed by a whale. The militants claim that such mosques have become places for apostasy, not prayer.
Since the Islamic State launched their blitz across Iraq, more than a million people have fled their homes, according to the United Nations. Many of those people have escaped to the semi-autonomous Kurdish region in northern Iraq since it has remained relatively stable since the 2003 US-led invasion.
In a statement published on Kurdish state media late on Saturday, Kurdish Regional Government President Massoud Barzani said the bombing of churches and mosques in Mosul "is against all the principles of the heavenly religions, humanity, and it is targeting the culture and demographic of the area".