ERBIL, Iraq (Reuters) - Four Iraqi aid workers and at least seven civilians were killed by indiscriminate mortar fire this week during aid distribution in two separate incidents in eastern Mosul, the United Nations said on Thursday.
A U.N. statement did not assign blame for the attacks, but Islamic State militants retreating from the Iraqi military's offensive in the northern city have repeatedly shelled "liberated" areas, killing or wounding scores of residents fleeing in the opposite direction.
The operation in Mosul, the jihadists' last major stronghold in Iraq, has retaken a quarter of the city but the troops' advance has been slow and punishing. The U.S.-backed campaign launched by a 100,000-strong alliance of local forces on Oct. 17, has become the biggest in Iraq since the 2003 U.S.-led invasion that toppled Saddam Hussein.
Lise Grande, U.N. humanitarian coordinator for Iraq, condemned the attacks as a violation of humanitarian principles.
"People waiting for aid are already vulnerable and need help. They should be protected, not attacked," she said. "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."
The authorities do not release figures for civilian or military casualties, but medical officials have said dozens of people are wounded each day in the Mosul battle.
Reporting by Stephen Kalin; Editing by Alison Williams