Fine Gael exit poll puts Yes vote at 60 per cent
Turnout Dublin and Munster in the Lisbon Treaty referendum is substantially up on last year, in contrast to many other parts of the country, where it was described as "slow and low".
The total turnout across the 43 consitutuencies was reported to be about 50 per cent by the time the polls closed at 10pm after being open for 15 hours.
A premlinary national exit poll by Fine Gael suggests the Yes side, with about 60 per cent, have scored a victory over the No side, who are on 40 per cent.
A spokeswoman for the Dublin city returning officer said voter turnout across the six constituencies averaged 44 per cent at 7pm. This contrasted sharply with other parts of the country, where turnout was as low as 10 per cent in several areas at lunchtime.
The turnout was said to be particularly strong in Dún Laoghaire, which had the biggest vote in favour of the treaty in 2008. It was also high in Dublin South West, one of the constituencies with the biggest No vote last year.
The turnout in commuter counties in Leinster, which have large populations of people working in Dublin, showed a sharp rise tonight and is as high as 60 per cent in some areas.
Polling across all five Cork constituencies seemed to be broadly on a par with the 2008 referendum, with turnout averaging approximately 50 per cent.
There was also a surge in turnout in many areas of Connacht. About half of all voters have cast their ballots in Galway. In Carlow and Kilkenny, turnout was estimated at just over 50 per cent in many areas tonight.
Taoiseach Brian Cowen cast his vote with his wife Mary shortly before 11am this morning at Mucklagh National School, Co Offaly.
President Mary McAleese and her husband Martin cast their ballots at St Mary's Hospital in the Phoenix Park at 10.30am.
Fine Gael leader Enda Kenny voted in his home town of Castlebar earlier at 9.15am while Libertas leader Declan Ganley voted at Briarfield National School near Moylough, Co Galway.
Counting of votes will begin tomorrow at 9am and the official result is expected in the early evening.
The Lisbon Treaty was rejected by a margin of 53.4 per cent to 46.6 per cent last year. Over three million people were entitled to vote in the referendum.