BAGHDAD (Reuters) – Islamic State claimed three suicide car bombs that killed at least 15 civilians and eight Iraqi policemen on Thursday in an eastern suburb of Mosul, according to a military statement.

The attacks targeted Kokjali, a suburb that the authorities said they had retaken from the jihadists almost two months ago.

A military spokesman said the car bombs went off in a market.

The U.S.-backed assault on Mosul, the jihadists’ last major stronghold in Iraq, was launched by a 100,000-strong alliance of local forces on Oct. 17. It has become the biggest military operation in Iraq since the 2003 U.S.-led invasion that toppled Saddam Hussein.

Islamic State militants 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.

Four Iraqi aid workers and at least seven civilians were killed by mortar fire this week during aid distribution in Mosul, the United Nations said on Thursday.

“People waiting for aid are already vulnerable and need help. They should be protected, not attacked,” said Lise Grande, U.N. 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.”

Elite army forces have captured a quarter of the city but the advance has faced weeks of fierce counter-attacks from the militants.

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.

(Reporting by Maher Chmaytelli; editing by Ralph Boulton)