Tens of thousands of South Sudanese danced and sang to mark their first hours of independence on Saturday, a hard-won separation from the north that also plunged the fractured region into a new period of uncertainty.

The Republic of South Sudan, an under-developed oil producer, became the world's newest nation on the stroke of midnight. It won its independence in a January referendum -- the climax of a 2005 peace deal that ended decades of civil war with the north.

Security forces at first tried to control the streets, but retreated as jubilant crowds moved in overnight and through the day, waving the new nation's black, red and green flags, dancing and chanting "South Sudan o-yei, freedom o-yei".

Huge crowds poured onto open ground around the site of the independence ceremony -- a headache for officials keen to guard dignitaries including the President of Sudan, the south's old civil war foe, Omar Hassan Al-Bashir.

Years of war have flooded South Sudan with weapons. Some revellers fainted in the blistering heat as they waited for South Sudan's parliamentary speaker James Wani Igga to read out an independence declaration in front of UN Secretary General Ban Ki-moon, Washington's UN envoy Susan Rice and the leaders of Nigeria, Tanzania and up to 30 other African states.

The crowd cheered as South Sudan President Salva Kiir unveiled a giant statue of civil war hero John Garang, the man who signed the peace deal with the north.     

In a possible sign of the South's new allegiances, the crowd included about 200 supporters of Darfur rebel leader Abdel Wahed al-Nur, whose forces are fighting Khartoum in an eight-year insurgency just over South Sudan's border in the north.

Earlier, the supporters of Nur's rebel Sudan Liberation Army faction stood in a line chanting "Welcome, welcome new state", wearing T-shirts bearing their leader's image. One carried a banner reading "El Bashir is wanted dead or alive".

Traditional dance groups drummed and waved shields and staffs in a carnival atmosphere. "I am very pleased," said Joma Cirilow, 47, his hand on his son's shoulder. "Do you want to be a second class citizen? No, I want to be a first class citizen in my own country."     

"Today we raise the flag of South Sudan to join the nations of the world. A day of victory and celebration," Pagan Amum, the secretary general of the South's ruling Sudan People's Liberation Movement (SPLM) told Reuters.     

"Free at last," said Simon Agany, 34, as he walked around shaking hands after midnight -- the time when officials said the South actually became the world's newest nation. "Coming away from the north is total freedom".             

North Sudan's Khartoum government was the first to recognise the new state on Friday, hours before the split took place, a move that smoothed the way to the division of what was Africa's largest country.

Egypt also recognised South Sudan on Saturday. Egypt has watched the split warily as it depends on the Nile's water to survive. The creation of South Sudan adds a new state on the river that could join East African states which have argued for a review of colonial-era quotas for the use of Nile water. - Reuters