The seismic change that will be remembered will be the historic shakeup of the Irish political party system.

Polls and tallies suggest a drop in support for Fine Gael - led by Leo Varadkar - and a rise in support for Sinn Féin.

Here are brief profiles of the main Irish political parties.

Sinn Féin leader Mary Lou McDonald is expected to arrive at the RDS count centre shortly and there is a huge media presence awaiting her. We think she will turn up at about 15:00.

Noel Rock has been a Fine Gael TD for Dublin North West since 2016 but he has conceded and will not be back in the Dáil.

Chris Page
BBC News Ireland correspondent

No results have been declared yet – but from the tallies at count centres around the country, it seems clear a huge shift has taken place.

The figures, which have been gathered by party teams as ballot boxes have been opened, strongly suggest the Sinn Féin surge has materialised.

Mary Lou McDonald’s party is challenging the main historical rivals – Fine Gael and Fianna Fáil – in the race for first preference votes.

Image source, PA

While Sinn Féin has been well used to electoral success in Northern Ireland – where it’s well established as the second largest party – it has never before matched the two parties which until now have been known as the “big two” in the Republic of Ireland.

Sinn Féin’s director of elections, Pearse Doherty, has told RTÉ that Mary Lou McDonald has begun to engage with other party leaders – and that there is “an onus to bring about change”.

But a senior Fine Gael minister, Richard Bruton, has re-iterated his party’s position it will not go into government with Sinn Féin.

During the campaign, Fianna Fáil also strongly ruled out a coalition with Sinn Féin.

Image source, Ben Stansall/AFP via Getty Images

Tallies show that Sinn Féin leader Mary Lou McDonald is on 36% of the vote in Dublin Central.

That level of support for a single candidate has not been seen there since Bertie Ahern in 2007, who was the leader of Fianna Fáil and taoiseach at the time.

The result could mark a major setback to Fianna Fáil's efforts to make gains in the capital.

Fianna Fáil general secretary Sean Dorgan said the party was "a little bit disappointed" that its vote in Dublin had been more "sluggish" than it had hoped for.

The deputy political editor of the Irish Times has been told we might see Sinn Féin in government after all.

Throughout the campaign both Fianna Fáil and Fine Gael said they would not go into government with Sinn Féin, but that may change as the full picture of the election becomes clear.

Image source, Paul Faith/AFP via Getty Images

Fine Gael has been in power since 2011.

It first entered government in coalition with Labour, but when Labour suffered huge losses in the 2016 election, Fine Gael instead formed a government with the support of Fianna Fáil - in a confidence and supply agreement - and independents.

2016 was the first time Fine Gael had topped the poll in successive general elections.

Louise Cullen
BBC News NI

As the tallies start to roll in, the predictions of a good day for Sinn Féin appear to be coming true.

Fine Gael leader Leo Varadkar is being outpolled in his constituency of Dublin West, while tally staff here at the RDS say the party leader Mary Lou McDonald is comfortably topping the poll in Dublin Central.

But there’s a long road between tallies and forming a government.

The earliest actual results are expected this afternoon but the count will last into the coming week.

With both Fine Gael and Fianna Fáil, having ruled out going into coalition with Sinn Féin, negotiations to form a government will be protracted.

Image source, Jeff J Mitchell/Getty Images

While an exit poll should never be taken as a perfect prediction of election results, it does point to a very different trend in Irish politics.

If the numbers come close to what was produced in the exit poll, the days of the reoccurring two party contest between Fine Gael and Fianna Fáil have ended.

The exit poll suggests these two parties now have the support of less than half the electorate.

Meanwhile, Sinn Féin, which only last year lost seats in Ireland's local elections, has surged ahead and the exit poll suggests it is tied with Fianna Fáil and Fine Gael for the first time.

Shane Harrison
BBC NI Dublin correspondent

Image source, Charles McQuillan/Getty Images

Analysis:

As Ireland north and south is battered by Storm Ciara, it is Storm Mary Lou that is the talking point of the Republic of Ireland's election.

Mary Lou McDonald and Sinn Féin have ensured that what was once a predominantly two party system is no more as she and her colleagues capitalised on public concern about health care and housing.

But Sinn Féin did not run enough candidates to capitalise on its unexpected surge in support.

With both parties ruling out coalition with Sinn Féin, it may take some time to form a government.

And Mary Lou McDonald will need little reminder of how fickle the electorate can be.

In the past, the Labour Party surfed the mood of change with the 1992 Spring Tide and the 2011 Gilmore Gale: neither lasted very long.

But this time it might be different.

The electorate have spoken but it might take some time to figure out what voters have said.

It's worth noting that there's still a bit of a health warning around the exit poll, which focuses on first preference votes only, although the earliest tallies paint a picture that reflects the exit poll results

Ireland's elections are carried out under the proportional representation (PR) voting system, using the single transferable vote (STV). Voters write "1" opposite their first choice candidate, "2" opposite their second choice, "3" opposite their third choice and so on.

This means that the picture presented when the first preference votes are counted does not completely reflect the final outcome.

Sinn Féin also ran 42 candidates across the 39 multi-seat constituencies, about half that of both Fine Gael and Fianna Fáil, which will have a knock-on effect on the number of seats it can secure.

Image source, AFP

There are 515 candidates running in 39 constituencies and 160 TDs will be returned to the 33rd Dáil (Irish parliament)

The outgoing Ceann Comhairle (Speaker), Seán Ó Fearghaíl has been automatically re-elected.

Here are some profiles of Ireland's political parties.

Image source, Oireachtas

Counting began at 09:00 local time as ballot boxes from across the Republic's 39 constituencies were opened.

An exit poll, commissioned jointly by Irish national broadcasters RTÉ and TG4, as well as The Irish Times and University College Dublin - indicates Fine Gael, led by Taoiseach (Irish Prime Minister) Leo Varadkar, Fianna Fáil and Sinn Féin on a virtual tie at about 22% for first preference votes.

Good afternoon and welcome to BBC News NI's live page of the Irish general election count. Stay with us throughout the day for all the twists and turns as we bring you results as they come in, along with analysis from our reporters and correspondents.

Image source, Getty Images