The opinion poll has swung slightly in favour of the No side during the election campaign. Turnout is expected to be high, so the vote count could be a shocker.
It's pretty even, but I'm always optimistic," Foreign Minister Thorgerdur Katrin Gunnarsdottir, who hopes for a yes, told AFP.
The referendum is only advisory and Icelanders are not voting directly on EU membership, but on whether the country should resume accession negotiations that were put on hold in 2013. The polling stations close at midnight Swedish time.
