The SDLP has taken the South Belfast constituency from the Ulster Unionist Party, in the second Westminster seat to be declared in Northern Ireland.
Alasdair McDonnell said he wanted to restore pride to Belfast
Alasdair McDonnell got 10,339 votes, with Jimmy Spratt of the DUP coming in second place with 9,104 votes.
DUP leader Ian Paisley has retained his seat in North Antrim with 25,156 votes and Sinn Fein's Gerry Adams has held onto his West Belfast seat.
Nigel Dodds, DUP, has held onto his North Belfast seat with 13,935 votes.
The DUP is also tipped to take East and South Antrim from the UUP.
After his election, Mr McDonnell said: "I want to thank the people of South Belfast who have sent a loud and clear message that tribal politics is not the only way forward in Northern Ireland.
"I believe we have a major task to do to restore this once great city to the sense of pride and dignity that it possessed."
Counting is in full swing in Northern Ireland
Mr Paisley said of his re-election: "That is democracy in action, people should listen and heed the voice of the people."
Meanwhile, a close supporter of David Trimble has said the Ulster Unionist Party has to prepare itself for the resignation of its leader, given the situation which is unfolding at the Upper Bann count.
David McNarry said this was likely to happen within 48 hours of the election result coming in.
In East Antrim, UUP sources have conceded that the DUP's Sammy Wilson is out in front while, in South Antrim, David Burnside of the UUP has appeared despondent because of a lower than hoped for turnout.
His rival, William McCrea of the DUP, said he was "quietly confident".
"It is certainly looking quite good," he said.
Earlier, Gerry Adams retained his West Belfast seat with 24,348 votes and the SDLP's Alex Attwood came second with 5,033 votes.
Mr Adams was confronted by two of the Omagh relatives as he arrived at the count in Belfast City Hall. He made no comment to the protestors.
Gerry Adams was the first MP elected in Northern Ireland's count
After the result was announced, Mr Adams said: "We stood on this election on three main planks.
"It was about dialogue. When others were negative, we gave hope.
"It was about getting the Good Friday Agreement and the peace process back on track and it's about a united Ireland."
DUP candidate William Hay has said some unionists voted tactically in an attempt to prevent Sinn Fein from winning the Foyle seat.
Mr Hay said he had been at several polling stations in the city and was in no doubt that tactical voting took place.
Ballot boxes across NI were opened at about 0900 BST to be verified, before counting started.
The counting of papers in the local council election does not begin until Monday.
A total of 918 people are competing for 582 council seats.
Counting for the Westminster seats is expected to continue late into Friday.