The pound collapsed to a 31-year low as currency, equity and oil markets went into freefall Friday with early referendum results indicating Britain would leave the European Union.

Sterling collapsed more than nine percent to $1.3466, its weakest level since 1985, while the greenback itself slumped below 100 yen for the first time in two-and-half years as traders fled to safety.

In the weeks leading up to Thursday's historic vote, there had been widespread warnings that a vote to leave the bloc would cause another rout across global markets that would wipe trillions off valuations, just months after a painful China-fuelled sell-off.

And as results came in, the doomsday scenario seemed to be unfolding.

The pound had earlier topped $1.50 following predictions the "remain" group would win but as the "leave" camp continued to post victories around the country, traders put in sell orders. The dollar slumped briefly to 99.02 yen, the first time it has gone below 100 yen since November 2013.

The Japanese unit is considered a safe bet in times of uncertainty and turmoil.

The seemingly likely outcome in favour of exiting has upturned expectations, which had been for a tight race narrowly won by the "remain", while bookmakers had said there was a 90 percent chance of staying in.

Highlighting the volatility across all markets, betting giant Ladbrokes tweeted: "Without doubt the craziest, fastest moving political betting market in recent history."

On equity markets Tokyo was down 6.7 percent, Hong Kong tumbled 3.6 percent, Sydney shed more than three percent and Seoul was 1.5 percent off. Shanghai and Singapore each sank 1.4 percent, while Taipei, Wellington, Manila and Jakarta all saw sharp losses.

- Oil plunges -However, volatility remains high as analysts say the vote is still too close to call, with much of London -- considered in favour of staying -- still to return results.

"After the early confidence, we could be getting a dose of realism that's causing some reasonably skittish market movements," Jeremy Stretch, head of foreign exchange strategy at Canadian Imperial Bank of Commerce in London, told Bloomberg News.

"It does look like the margin between the two sides is going to be relatively tight, and accordingly sterling volatility is going to remain elevated until we get a more definitive picture."

With many financial groups believed to have conducted their own exit polls, there is a worry among traders that the fall in the pound could indicate Britain is on its way out of the economic bloc.

In the early hours in Britain, Nigel Farage, leader of the anti-Europe UK Independence Party, declared victory, saying it was the country's "independence day".

The prospect of a severe hit to the global economy also hammered oil prices, with both main contracts slumping more than five percent.

"We are seeing oil swept up in the general market nervousness to the vote," Ric Spooner, a chief analyst at CMC Markets in Sydney, told Bloomberg News.

"Corrections are likely to be fairly shallow in oil because prices will be supported by the fact a balanced market is firmly on the horizon."

- Key figures around 0330 GMT -Pound/dollar: DOWN at $1.3527 from $1.4974 late Thursday

Euro/dollar: DOWN at $1.1030 from $1.1422

Dollar/yen: DOWN at 101.77 yen from 106.53 yen

Tokyo - Nikkei 225: DOWN 6.7 percent at 15,123.44

Shanghai - Composite: DOWN 1.5 percent at 2,848.31

Hong Kong - Hang Seng: DOWN 3.6 percent at 20,110.64

New York - DOW: UP 1.3 percent at 18,011.07 (close)

London - FTSE 100: UP 1.2 percent at 6,338.10 (close)