Mortar rounds fired by Islamic State militants have killed 16 civilians in areas of Mosul already retaken by troops, Iraqi military and hospital officials say.

They said the bodies of the 16, killed overnight and early on Saturday, have been taken to military hospitals in eastern Mosul.

An Associated Press team in eastern Mosul on Saturday said scores of civilians are continuing to stream out of the inner areas of the city to escape the fighting, making their way to camps for the displaced.

The UN refugee agency UNHCR says at least 73,000 Iraqis have fled Mosul since the government's campaign to retake the city began on October 17.

AP