South Sudan turned the world's newest country and Africa's 53rd state on Saturday.
Sudan's President Omar al-Bashir and UN secretary general Ban Ki-moon were among the international dignitaries attending the celebrations in the capital, Juba, BBC reported.
The birth of the world's newest nation followed a process made possible by the 2005 peace deal that ended a long and bloody civil war.
A referendum, under the Comprehensive Peace Agreement, was held on independence, which was favoured by more than 99 percent of voters.
The new country is rich in oil, but one of the least developed countries in the world, where one-in-seven children dies before the age of five.
The south's independence followed decades of conflict with the north, in which some 1.5 million people died.
Earlier, Sudan became the first state to officially recognise its new neighbour South Sudan.
Khartoum, the capital of Sudan, officially recognised the independence of South Sudan a day before it was to officially become Africa's 53rd state after a five-month transition period.
"The Republic of Sudan announces that it recognises the Republic of South Sudan as an independent state within the borders defined on January 1, 1956," said minister of presidential affairs Bakri Hassan Saleh on national TV Friday.
