The former rebel Sudan People’s Liberation Movement cited its own estimates for the achievement which has to be officially confirmed by the South Sudan Referendum Commission that is organising the week-long vote.
But there were long queues at polling stations again on Wednesday as voters responded to calls from the party for a “100 per cent turnout”.
A referendum commission spokesman said the SPLM’s claim was “quite possible. It could even be higher.”
“Voting is an honour to those who sacrificed their lives so we can have this choice today,” she said, referring to the devastating 1983-2005 civil war with the north in which an estimated two million people died.
“It is a great opportunity that will not happen again.”
Loudspeaker trucks criss-crossed the potholed dirt tracks of Juba urging voters to respond to the call.
“It is important that you go out to vote, have your cards with you. You have only three days more, freedom can’t wait,” the hailers intoned to the accompaniment of loud African music.
The shine was taken off the party mood by the deaths of 10 southerners returning from the north for the referendum in an ambush by heavily armed Misseriya Arab tribesmen on Monday.
The attack was the latest incident in an upsurge of violence over Abyei, a disputed district on the north-south border where the nomadic Misseriya are engaged in bitter clashes with pro-southern Dinka farmers over the its future, which have claimed at least 33 lives since Friday.