"The capital punishment was carried out this morning at 10:30 am (0630 GMT) on three convicts. They were hanged to death," Kubba said Thursday.
The three, believed to be members of Al-Qaeda linked extremist group Ansar al-Sunna, were sentenced in May for killing and kidnapping policemen and raping Iraqi women.
Their sentences were approved by the Supreme Council for Justice, the highest judicial authority in Iraq, although President Jalal Talabani, a vocal opponent of capital punishment, had refused to sign the death warrants.
The three convicted men were Kurd Bayan Ahmad al-Jaf, a 30-year-old taxi driver, as well as two Sunnis, Oudai Dawud al-Dulaimi, a 25-year-old builder, and Taher Jassem Abbas, a 44-year-old butcher.