Veteran politician Beji Caid Essebsi declared victory in Sunday's presidential run-off vote, seen as the last step in Tunisia's shift to full democracy four years after an uprising ousted autocrat Zine El-Abidine Ben Ali.

Official results are not due until Monday and his rival, the incumbent president, Moncef Marzouki, refused to concede defeat.

But soon after polls closed, Essebsi, an 88-year-old former parliament speaker under Ben Ali, announced that he had won by a clear margin and jubilant supporters took to the streets of the capital in celebration, chanting "Beji President!"