FACTBOX: Violence stalks troubled Sudan

(Reuters) - Sudan cut diplomatic relations with Chad on Sunday after an attack on the Sudanese capital by Darfur rebels which it said was supported by Chadian President Idriss Deby.

Here are some key facts on Sudan and its conflicts:

* Sudan is Africa's largest country with an area of 2.5 million sq km (967,500 sq miles). It straddles the middle reaches of the Nile and is bordered by Egypt to the north; the Red Sea, Ethiopia and Eritrea to the east; Kenya, Uganda and the Democratic Republic of Congo to the south; and the Central African Republic, Chad and Libya to the west.

* Oil exploration began in the 1970s, but operations were repeatedly interrupted by war, with southern rebels laying claim to oil fields that provided the government with vital revenue.

* In 1983, the Sudan People's Liberation Army (SPLA), the main southern rebel group led by John Garang, launched a war against the northern-based government, partly sparked by the imposition of Islamic law, sharia, by the then-government.

* The war pitted the black African south, which is mainly Christian and animist, against the mainly Muslim, Arabic-speaking north. The war was complicated by tribal and factional fighting, as well as the conflict over oil.

* In 2004, a deal, sealed by the SPLA and the Khartoum government, cleared the way for a comprehensive peace to end the 21-year-old civil war in the south that claimed more than 2 million lives.

Darfur in the west:

* Rebels rose up against the government in February 2003 saying Khartoum discriminated against non-Arab farmers in Darfur in favor of Arab tribes. More than 2 million Muslim Darfuris, mainly subsistence farmers from a wide variety of ethnic groups for whom Arabic is a second language, have fled their homes.