The independence declaration was read out in front of dozens of heads of state and foreign dignitaries and tens of thousands of cheering southerners. South Sudan’s national flag was then raised to wild applause, tears and cheers.
The parliament speaker said that as a “strategic priority”, South Sudan would seek admission to the United Nations, the African Union, the east African bloc, Igad, and other international bodies.
Southern leader Salva Kiir then signed the transitional constitution and took the oath of office as the new state's first president,
Speaking for Igad, Kenya’s President Mwai Kibaki said the independence declaration was “an important…step in the search for lasting peace and stability for the people of the entire Sudan.”
President Barack Obama announced on Saturday that the US formally recognised the newly created republic and vowed to support it in the “hard work” of nation bulding.
Egypt has also officially recognised the new nation.
South Sudan's independence comes after more than 50 years of conflict between the southern rebels and successive Khartoum governments that left the region in ruins, millions of people dead and a legacy of mutual mistrust.
The 2005 comprehensive peace agreement that finally ended the conflict, and which was signed under intense pressure from foreign countries, particularly the United States, Britain and Norway, paved the way for a referendum on southern independence in January.
Around 99 per cent of southerners voted to split from the north.