* European Greens hail "green wave" after Dutch, Irish polls
* Early results suggest Greens big movers in local election
* Governing Fine Gael, opposition Fianna Fail hold steady (Updates after first seats filled)
By Padraic Halpin
DUBLIN, May 25 (Reuters) - Support for Ireland's Green Party surged in European and local elections, an exit poll showed on Saturday, putting it in line to take its first seats in the European Parliament for 20 years and make the biggest gains in county and city councils.
The Greens were set to win as many as three of the 13 European seats up for grabs and increase their local vote to 9% from less than 2% five years ago, according to a RED C exit poll for RTE/TG4, a showing that would put them in contention for government formation if repeated at a parliamentary poll.
After 90 of the 949 council seats were filled at 1000 GMT, early results suggested The Greens' performance was in line with the exit poll. In Dublin, some of their candidates topped polls by significant margins.
"We cannot yet count our chickens, but the exit polls for the Irish Greens are extremely encouraging," Irish Green Party leader Eamon Ryan said in a statement issued by the European Greens.
European Greens co-lead candidate Bas Eickhout talked of a "green wave" rolling on to Irish shores from the Netherlands, where GroenLinks' (GreenLeft's) share of the vote rose to 10.5%, according to an exit poll there.
While Ireland does not hold a significant share of the 751-seat EU chamber - and will initially send 11 MEPs until Britain actually leaves the bloc - an ebb in support for mainstream parties is raising hopes among Europe's Greens that they could act as kingmakers.
"It is those climate strikes, it is those young people standing up and saying we have to protect our future," Ryan told national broadcaster RTE.
The exit poll showed that almost 90% of voters feel that the government needs to prioritise climate change more.
Health Minister Simon Harris of the governing Fine Gael said the topic came up on the doorsteps more in the last six months than in all of his last eight years as a member of parliament, while Prime Minister Leo Varadkar said the government had got a very clear message from the public that they want it to do more.
Fine Gael and the two main opposition parties Fianna Fail and Sinn Fein looked set to share most of the remaining European seats with results set to be announced from Sunday.
In Varadkar's first electoral as Fine Gael leader, the exit poll put his party and fellow centre-right Fianna Fail level on 23%, both down slightly on 2014 when Fianna Fail emerged as the biggest party. That set it up to close the gap on its main rival in parliamentary elections two years later.
The left wing Sinn Fein was set to fall to 12% from 15%, and while the estimates suggested a further slight fragmentation of party support, it showed continued strong backing for centrist political parties in the EU's most committed member state.
"In a lot other European countries, the far right in particular is encroaching very significantly and that isn't the case here. In general terms, it looks like the centre parties have done reasonably well," said Theresa Reidy, a politics lecturer at University College Cork.
(Additional reporting by Philip Blenkinsop in Brussels; editing by Helen Popper and G Crosse)
Our Standards: The Thomson Reuters Trust Principles.