Britain's bitterly contested referendum on whether to quit the European Union was too close to call on Friday as early results showed a deeply divided nation while the pound was hammered on financial markets.

Bookmakers adjusted their odds to reflect an even chance of a 'Brexit' as the Leave camp grabbed an early lead, before results from Glasgow and parts of London helped the Remain side to inch ahead as a nail-biting national count proceeded.

With results declared from 103 of 382 voting districts plus parts of Northern Ireland, Remain was ahead by 50.6 percent to 49.4 in the referendum, in which a vote to break with Europe could usher in deep uncertainty over trade and investment and fuel the rise of anti-EU movements across the continent.

Initial results suggested those in favor of quitting the EU were outperforming pollsters' expectations. They scored close to 70 percent of the vote in Hartlepool in northeast England and in Basildon, near London.

It was not clear whether an expected pro-EU vote in the capital would be sufficient to redress the balance.

"I think this could be extremely close. There is a disaffected vote," said John McDonnell, finance spokesman for the opposition Labour Party, which had favored a vote to Remain.

"People are concerned about how they have been treated with austerity and how their wages have been frozen for about seven years. A lots of people's grievances have come out and we have got to start listening to them."

Sterling swung wildly, initially rising on expectations of a Remain win but then tumbling by nearly 10 cents. It later trimmed some of its losses but was still three percent down on the day by 0200 GMT. (Reuters)