The U.S. Department of State 2009 International Religious Freedom Report on Sudan estimated the country's Muslim population at 70 percent. Muslims constituted the overwhelming majority in the North, although there were sizable Christian communities in the major cities, especially Khartoum. Sudanese who believed in traditional religions and Christians predominated in the South. The 1998 constitution provided for freedom of religion but treated Islam as a state religion and cited sharia as one of the sources of legislation. Differences over the application of sharia for non-Muslims were one of the root causes of the civil war between the North and the South. As a result, with an end to the conflict, the Interim National Constitution underscored the diversity of religious beliefs in Sudan.