Observers in Dublin say it looks like the No camp has the early edge in the Lisbon Treaty vote count.
No results have been officially released, but politicians in the Yes camp have been expressing concern about the outcome.
The No vote appears to be particularly strong in large urban areas like Cork and Dublin, but no clear pattern has emerged as yet.
Speaking at the Dublin count centre in the RDS, former Fine Gael leader Garrett Fitzgerald said the situation looked very uncertain, with a large divide between middle-class and working-class areas.
Labour Party TD Joan Burton, meanwhile, said it was looking like "quite a high No vote" in the capital.