May 11 (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 favour 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.

* Justice and Equality Movement (JEM) and the Sudan Liberation Army (SLA) were among the first rebel groups to emerge.

* Arab militias, some known as the Janjaweed, have driven farmers from their land in a campaign rights groups say amounts to ethnic cleansing and the United States has called genocide.

* The Sudanese government has said the Janjaweed are outlaws and has vowed to disarm them.

* Experts estimate about 200,000 have died from disease, starvation and violence. Khartoum says about 10,000 people have died.

Border trouble.

* Sudan's relations with Chad have been deteriorating for some time. The long and porous border with Sudan's Darfur has long been a base for rebels from both nations to stage attacks against their central governments.

In 2008 Chadian rebels, which the Chad government said were supported by Sudan, attacked N'Djamena. The attack, which failed, was swiftly followed by Khartoum's offensive against three towns held by rebels that Sudan said were supported by Chad.

* There are more than 240,000 Darfur refugees being housed in United Nations' camps located along a 600-kilometre stretch of the Chad-Sudan border. (For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com/)

AlertNet news is provided by