PRESS ASSOCIATION -- South Sudan has raised the flag of its new nation for the first time, as thousands of South Sudanese citizens and dozens of international dignitaries swarmed the new country capital of Juba to celebrate the country's birth.

South Sudan became the world's newest country with a raucous street party at midnight. At a packed midday ceremony on Saturday, the speaker of parliament read a proclamation of independence as the flag of Sudan was lowered and the flag of South Sudan was raised, sparking wild cheers from the crowd.

"Hallelujah!" one resident yelled, as other wiped away tears.

UN Secretary-General Ban Ki-moon, former US Secretary of State Colin Powell and dozens of other world leaders were in attendance under a blazing sun as South Sudan President Salva Kiir hosted the noon-hour ceremony. Sudan President Omar al-Bashir, a deeply unpopular man in Juba, arrived to a mixture of boos and surprised murmurs.

"Wow, this is a great day for me because it's a day that reflects the suffering that all southerners have had for almost 50 years," said David Aleu, a 24-year-old medical student.

Thousands of South Sudan residents thronged the celebration area, and organisers soon learned they did not have enough seats for all the visiting heads of state and other VIPs. The heat was strong enough that Red Cross workers attended to many people who fainted.

"We're overwhelmed. We did not know that the whole world was going to join us in our celebration," the ceremony's announcer said.

The black African tribes of South Sudan and the mainly Arab north battled two civil wars over more than five decades, and some two million died in the latest war, from 1983-2005. It culminated in a 2005 peace deal that led to the independence declaration.

Thousands of South Sudanese poured into the ceremonial arena when gates opened. Traditional dancers drummed in the streets as residents waved tiny flags.

Activists from the western Sudan region of Darfur, which has suffered heavy violence the past decades, held up a sign that said "Bashir is wanted dead or alive". Mr Bashir has been indicted by the International Criminal Court for war crimes in Darfur.

William Hague, the British foreign secretary, said in a statement sent to the Huffington Post, that Saturday's move "represents the triumph of peaceful negotiation over conflict and adversity, and is a moment of hope and optimism for the future".

Speaking from Juba, the capital, he said:

The government of the United Kingdom stands with the people of South Sudan as they seek a future of stability and prosperity; one we hope of lasting peace with their neighbours, full integration into the region, and strong cooperation with Britain and other nations represented here today. We look forward to South Sudan taking its place as a full member of the United Nations.

We pay tribute to the enormous progress South Sudan has made since the signing of the Comprehensive Peace Agreement six and a half years ago.

I commend all those in North and South who have been part of the painstaking negotiations that brought us to this point.

The people of the Republic of South Sudan and the Republic of Sudan now have a chance to coexist peacefully as neighbours and to settle their remaining differences.

We urge the leaders of both countries to maintain their commitment to the continuing negotiations, which are essential to building a lasting peace for all the peoples of both Sudans, and to lose no time in addressing the considerable challenges which still remain.

They will have the support of the Britain and the international community as they do this.