Early results from southern Sudan's referendum on independence show the region has voted overwhelmingly to split from the north and form a new country.

Reports at the first 10 ballot sites where votes have been counted indicate support for separation is greater than 90 per cent.

More than 83 per cent of those who registered turned out to cast their ballots.

Election observers have labelled the referendum exemplary.

"This procedure has happened in a very peaceful, secure and very well organised manner," European Union election observer Martin Ehrenhauser said.

At one of the first polling stations where ballots were counted, more than 3,000 votes were cast in support of secession. Only 25 votes were in favour of the north and south staying together.

That pattern is playing out at ballot stations across the south's main city, Juba.

If the process stays on track, South Sudan could become the world's newest nation by July.

The official result is not likely to be declared until next month.

Experiencing peace

Thousands of South Sudanese have returned home in recent weeks and that number could double.

Dr Justin Tongun fled Sudan as a teenager. First he had to escape Juba, which was under siege.

He then spent months on foot trying to hide from forces that were roaming the country as he walked south.

It took him a year to walk the 500 kilometres to safety in Uganda.

Dr Tongun came back the moment he heard a peace agreement had been signed. He is now experiencing something he never thought possible - peace.

"I've never known what is peace except for these five years. This is an opportunity that we'll never hear guns again; we'll never run again," he said.

He has one message for any South Sudanese who may have gained medical skills in exile.

"Please come back home. Home is sweet. Things are nice. We are safe. We are doing fine. We need your service. Come and help your people," he said.

The list of challenges facing Sudan appears endless.

In one of the least developed countries on Earth, this is a chance to build a new nation from the ground up.