Clashes between south Sudan's Army and rebel militiamen killed at least 55 people, a government official said on Sunday in the soon to be independent state gripped by a bloody wave of unrest.

A spate of attacks by rebels against the South Sudanese Army in the region's troubled Jonglei state killed 105 people, 39 of them civilians, an army spokesman said on Friday, leaving a hard-won truce in tatters.

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.

South Sudan's ruling party said Wednesday that the 60-per cent turnout threshhold required for a landmark independence vote to be valid has been reached after just three days of polling.

Southern Sudanese flocked to the polls once again on Tuesday, the third day of voting in the referendum on independence for the south, bringing the region a step closer to nationhood.