The unity of the United Kingdom has been called into question as a top political party in Northern Ireland has alluded to a possible independence referendum.
The UK voted to leave the EU, but Northern Ireland voted to remain, sparking a response from Sinn Fein.
Sinn Fein chairman Declan Kearney said in a statement: "This outcome tonight dramatically changes the political landscape here in the north of Ireland and we will be intensifying our case for the calling of a border poll.
"The British government as a direct result have forfeited any mandate to represent the interests of people here in the north of Ireland in circumstances where the north is dragged out of Europe as a result of a vote to leave."
The comments also come after First Minister Nicola Sturgeon issued a statement that said the Scottish people see their future within the EU.
The Scottish National Party had in their manifesto a pledge for a second independence referendum if there was a material change, including the UK voting to leave the EU but Scotland voting to remain.
The question of unity in both Northern Ireland and Scotland had been raised before the vote, but the preparation will do little to console Prime Minister David Cameron.
While 84 Tory MPs wrote to Cameron last night asking him to stay on in the event of Brexit, speculation continues over whether he has enough confidence in him.
Meanwhile, Labour has questions of its own to answer, with a number of high profile MPs having warned it has alienated its own party by campaigning for the UK to remain in the EU.