The state religion is Islam, whose adherents, primarily Sunni, are estimated to constitute from 65% to 75% of the population; most of them live in the north. As an important transit station for Mecca-bound African pilgrims, Sudan remains intimately linked with the Islamic world. There are sizable minorities of Christians and practitioners of traditional indigenous religions, particularly in the south, where Christianity is reported to be growing rapidly. Most of the Christian community are professed Roman Catholics. Greek Orthodox, Coptic, and Anglican Christians are found in small numbers in towns. There is reported evidence, however, that many Christians continue to practice elements of traditional indigenous religions.
Among the Muslims, religious brotherhoods (tarigat) play an important role in sectarian and communal life. The two most popular brotherhoods are the Ansar, which is closely associated with the Umma Party, and the Khatimia, which is associated with the Democratic Unionist Party.
The 1973 constitution guaranteed unrestricted freedom of religion, but Islam was cited as the official religion. Christian mission schools in the south were nationalized in 1957, and foreign missionaries were expelled from the south in 1963–64. At present, religious organizations are subject to the 1994 Societies Registration Act, which replaced the controversial 1962 Missionary Societies Act. Theoretically, it allows churches to engage in a wider range of activities; however, churches are subject to the same restrictions placed on nonreligious corporations. Religious groups must be registered and approved in order to be recognized or gather legally. In recent years, the Roman Catholic Church has not been given permission to build any new churches; however, other Christian groups have been granted such permission.
The civil war that resumed in 1983 is largely religious. The government is dominated by northern Muslims while southern rebel groups are mostly Christians and traditionalists. The government, which claims Islam as the state religion, supports adherence to Shari'ah (Islamic) law and has declared a jihad, or holy war, against the rebel factions. The primarily Christian rebel group, the Sudan People's Liberation Movement (SPLM) supports a secular government, but seems willing to allow Shari'ah law in the northern states.
The government and Muslim majority continue to discriminate against and persecute non-Muslims. Many non-Muslims have been fired from jobs in civil service and non-Muslim business owners are often harassed and discriminated against in matters of government contracts and trade licenses. Students of Christian schools are often kept from completing their compulsory military service, which is required in order to move on the University. Many Muslim employers do not allow Christian employees time off to attend Sunday worship services. Throughout the civil war, several non-Muslim women and children have been captured by Muslims, sold into slavery and forced to convert to Islam. Conversion from Islam to any other religion is punishable by death.