GENEVA, Aug 23 (Reuters) - Hundreds of thousands of Iraqis in and around Mosul could be uprooted by the military assault to retake city from Islamic State, the U.N. refugee agency UNHCR said on Tuesday.

"In Mosul we believe the displacement situation may be about to dramatically worsen," UNHCR spokesman Adrian Edwards told a briefing, saying the agency needed more land for camps.

"The humanitarian impact of the military offensive is expected to be enormous, up to 1.2 million people could be affected."

(Reporting by Stephanie Nebehay; Editing by Robin Pomeroy) ((Stephanie.Nebehay@thomsonreuters.com; +41 22 733 3831; Reuters Messaging: stephanie.nebehay.thomsonreuters.com@reuters.net; twitter @StephNebehay))