Isis car bombs have killed 23 people in a district of Mosul recently liberated from the extremist jihadi group.
Eight of the dead were policemen and 15 were civilians, according to the Iraqi Defence Ministry.
Iraqi troops entered Gogjali, in the east of Mosul, in early November.
Three suicide bombers were behind the attack in the district, Isis said when it claimed responsibility.
Also on Thursday, four Iraqi aid workers and at least seven civilians were killed when a mortar attack hit a distribution of aid in the city.
It was the second attack on aid workers and civilians in less than a week.
Three vehicle-borne improvised explosive devices went off in Kokjali, an eastern suburb that the authorities said they had retaken from the jihadis almost two months ago.
At least two civilians were killed and 20 others wounded, including soldiers, according to local police, a health official and a witness. The death toll was expected to rise.
A UN statement on the two separate mortar attacks this week that killed aid workers and wounded about 40 people said indiscriminate shelling violated international law.
“People waiting for aid are already vulnerable and need help. They should be protected, not attacked,” said Lise Grande, UN humanitarian coordinator for Iraq.
“All parties to the conflict – all parties – have an obligation to uphold international humanitarian law and ensure that civilians survive and receive the assistance they need.”
She did not assign blame for the attacks, but Isis fighters retreating from the military offensive have repeatedly shelled areas after they are retaken by the army, killing or wounding scores of residents fleeing in the opposite direction.
The US-backed assault on Mosul, the jihadis’ last major stronghold in Iraq, was launched by a 100,000-strong alliance of local forces on 17 October. It has become the biggest military operation in Iraq since the 2003 US-led invasion that toppled Saddam Hussein.
Elite army forces have captured a quarter of the city but the advance has faced weeks of fierce counter-attacks from the militants, even in areas thought to be cleared.
The authorities do not release figures for civilian or military casualties, but medical officials say dozens of people are wounded each day in the battle for Mosul.
Additional reporting by agencies.
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