Nairobi, Jan. 9 (Reuters): As bare-chested warriors danced and turbaned heads bowed in prayer, Sudan's Islamist government and southern rebels forged a comprehensive peace on Sunday ending Africa's longest-running civil war.

Sudan's First Vice-President Ali Osman Mohamed Taha and rebel leader John Garang signed the accord in Kenya's capital Nairobi, ending a 21-year conflict in the south that has killed an estimated two million people mainly by famine and disease.

The agreement did not cover a separate conflict in western Darfur area of Africa's largest country, where almost two years of fighting have created what the UN calls one of the world's worst humanitarian crises.

At the signing ceremony in a Nairobi sports stadium, bare-chested Dinka warriors wearing leopard-skin loincloths and white paint on their faces danced for thousands of banner-waving exiles and refugees who planned now to return home. 'If I had wings I would be flying,' said Grace Datiro, 35, a southerner who has lived in Kenya for 14 years since war drove her from her home in Sudan.

US secretary of state Colin Powell, attending the signing, urged Khartoum and the southern rebel Sudan People's Liberation Movement to work together immediately to end atrocities in Darfur, and said Washington would upgrade its ties with Sudan to a 'positive relationship' only when that was done.

'This positive relationship will only be possible in the context of peace throughout the entire country,' he said, urging both parties to keep promises made in the southern peace accord.

Washington has a special interest in Sudan, which it lists as a state sponsor of terrorism because of Khartoum's record of hosting militant Islamists including Osama bin Laden in the early 1990s, and maintains a range of economic curbs against it.

The UN Security Council ' meeting in Nairobi, away from its New York home for the first time in 14 years ' unanimously adopted a resolution in November promising political and substantial economic support once Sudan ended both wars.

The new agreement is expected to trigger the return of more than half a million Sudanese who fled to nearby countries and the gradual resettlement of four million displaced internally. 'Peace is going to bring our country abundance, welfare and benefaction,' said Sudanese President Omar Hassan al-Bashir.