Chanting and cheering, "Leave" supporters hailed early victories in the EU referendum at a lavish party in London featuring a large cake decorated with a champagne bottle and a Union Jack flag.

Whenever a Brexit result came in, champagne corks popped as campaigners shouted out the name of the region voting in their favour at the party in the Millbank tower block in Westminster.

"The eurosceptic genie is out of the bottle and it will now not be put back," UK Independence Party leader Nigel Farage said at the party.

"EU's finished, EU's dead," he said, as the cheerful crowd chanted: "Out! Out! Out!"

Arron Banks, a multi-millionaire funder of the pro-Brexit campaign, said: "I'm feeling quite confident. I think it's still all to play for."

The mood was far more subdued at the "Remain" party in London's Royal Festival Hall where supporters were glued to TV screens clutching beers -- some with their hands over their mouths.

At the Lexington bar in Angel in central London, where many "Remain" supporters had gathered, there was also a sense of suspense.

"It's tight. I do worry about the prospects of this country if we don't stay," said 20-year-old Harlan Matthews.

"I am concerned about the polarisation of the vote. Geographically, it appears to be divided."

Early results showed "Leave" victories in northern England and "Remain" wins in London.

"People in London have a different identity. We are Londoners first, then European, then British," said 33-year-old Beverly David.

"This is incredibly close. We have no idea where this is going to go," she said in the crowded bar, where some supporters wore "IN" shirts.

Julius Beltrame said: "This is a protest vote on an international scale. This is an inheritance of 30 years of neo-liberal economics."

"I never felt less British and more Londoner," the 39-year-old said.

Ian Buerger, 26, said he had voted "Remain" but really wanted to vote "Leave".

"There are legitimate arguments on both sides. The debate has been poisonous and it doesn't end tonight," he said.

- 'Win we must' -In Manchester, where the result was due to be declared in the 19th century town hall later on Friday, campaigners from both sides were in a tense wait in the glare of television lights.

"I'm very excited, there is definitely a buzz in the air, that's for sure and above all we don't have anything to lose," said Luke Thomson, chief of staff for a UKIP European Parliament lawmaker.

In case of Brexit, the 22-year-old admitted that he would lose his job since there would no longer be British MEPs but he said: "Yes that's fine, it's a price worth paying."

To him, the winning argument of the "Leave" campaign has been "democracy, without a doubt".

At a neighbouring table, "Remain" campaigners followed the results on their laptops.

EU supporter Neal Carmichael, Conservative MP for Stroud in Gloucestershire, said he was feeling relaxed.

"I feel excited, I feel optimistic," he said.

"We have a long way to go to be sure we have won, but win we must," he said.