In Iraq, about 2 million people have been displaced by the war and sectarian fighting. Aid groups estimate that nearly 500,000 of them are living in cities and towns as squatters.

U.N. officials say the Iraqi government and aid agencies are only now recognizing the magnitude of the problem. Some refugees have returned to find their homes occupied. Others were forced to flee violence as tensions between Sunni and Shiite Muslims erupted.

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