At least 16 people died when rebels attacked South Sudanese troops in troubled Jonglei state, breaking a ceasefire signed in January, a Southern Army spokesman said on Thursday.

South Sudan was set to wrap up a week-long independence vote on Saturday confident one of the world's poorest regions is now securely on the path to becoming its newest nation state.

The 60 per cent turnout required for a South Sudan independence vote to be valid has been met, and even surpassed, Souad Ibrahim, spokeswoman for the referendum commission told AFP on Thursday.