Salva Kiir, the leader of south Sudan's former rebel group the SPLM, has been sworn in as the first elected president of the semi-autonomous southern region.

It follows his landslide victory in April's elections, part of the peace deal that ended a 21-year civil war between north and south.

Next year, the people of Southern Sudan will vote on possible independence.

A BBC correspondent in Juba says it is widely believed that, given a free poll, they will vote in favour.

Most of Sudan's lucrative oil is in the south, and the exact boundary with the north still has to be defined.

The BBC's James Copnall in Juba says Mr Kiir is more of an old soldier than a natural politician.

But in becoming south Sudan's first elected president Mr Kiir faces huge political challenges, he says.

The region is one of the least developed on Earth - one of the reasons for long civil war that ended in 2005.

At his swearing-in ceremony, Mr Kiir did not advocate directly for either independence or continued unity.

But he did say the battle for unity has almost been lost - a heavy hint about which way he thinks southerners will vote.