At least 25 people have been executed gangland-style in Iraq's third-largest city this week, with residents gunned down in ones and twos and bodies found scattered throughout Mosul.
Elsewhere, five US troops were killed in operations south and west of Baghdad, the US military said on Thursday and police stormed a farm and freed 17 victims of a factory kidnapping.
Mosul, 225 miles northwest of Baghdad, has a mixed Kurdish and Sunni Arab population and a tradition of bad blood.
The Kurds, who are largely Sunni Muslim but not Arab, have formed a prosperous autonomous region nearby after decades of oppression and mass killings under the Sunni Arab minority that ran Iraq until Saddam Hussein was ousted three years ago.
Police said they were not sure if the attacks were carried out by the Sunni Arab-led insurgency, common criminals or sectarian death squads.
Increasing numbers of Iraqi deaths over the past months have been attributed to revenge killings carried out by Shiite-backed militia organizations or Sunni Arabs who have banded together in retribution.
The outburst of killings was first reported Tuesday morning when police found the bodies of a husband and wife -- both Kurds -- shot to death in eastern Mosul, according to police Capt. Ahmed Khalil. Before the day was out, 10 people were either killed in shootings or found dead.
The killings persisted on Wednesday, with eight people -- including a child and a college student -- shot to death by nightfall.
The violence continued on Thursday, said police Brig Abdel-Hamid Khalf, with a policeman killed in a firefight with gunmen early in the day and six civilians shot to death before sunset.
The police raid north of Baghdad that freed the 17 captives came a day after the mass kidnapping, believed to have been organised by Sunni extremists at the close of a factory shift.
Initial reports said as many as 85 people, including women who had taken their children to work, were initially taken.
But Industry Minister Fowzi Hariri told state-run Iraqiya TV on Thursday that 64 people were abducted, two of whom were killed trying to escape.
Thirty people, mainly women and children, were freed shortly after the kidnapping, leaving 15 still believed in captivity.