U.S. stock index futures dipped sharply lower as results from the Thursday UK referendum pointed to the nation leaving the European Union.
Dow Jones futures briefly saw an implied open down more than 400 points. After paring those losses briefly, futures then broke below an implied open down more than 700 around 12:35 a.m. ET (5:35 a.m. London time).
The S&P 500 and Nasdaq, meanwhile, were implied by futures to open down more than 5 percent.
The FTSE futures also extended their losses, pointing to a roughly 8 percent fall at the U.K. stock market open.
U.S. stocks closed more than 1 percent higher Thursday, with the pound near year-to-date highs against the dollar, following increased expectations the U.K. will vote to remain in the European Union.
The major indexes rallied into the close, with the S&P 500 above the psychologically key 2,100 level and posting its highest close since June 9.
The Dow Jones industrial average jumped about 230 points to close above the psychologically key 18,000 level for the first time since June 8. The S&P was about 1 percent below its all-time intraday high, while the Dow was within 2 percent of its all-time intraday high.
"I think the market's already voted. ... It looks like they're looking for the stay vote to prevail," said Adam Sarhan, CEO of Sarhan Capital.
"This could be a classic case of 'buy the rumor, sell the fact,'" he said.
Financials, which are also sensitive to the results of the EU referendum, gained 2.1 percent to lead all S&P 500 sectors higher. The Bank (KBE) and Regional Bank (KRE) ETFs closed nearly 3 percent higher or more for their best day in more than a month.
Goldman Sachs gained 3 percent to contribute the most to gains in the Dow. The U.S. Federal Reserve is set to release the first results from the annual bank stress tests after the close.
The pound traded near $1.490, its highest since December. The U.S. dollar index traded about 0.4 percent lower, with the euro near $1.138 after earlier hitting its highest in more than a month. The yen was near 105.9 yen versus the greenback, near its highest in a week.
The Dow transports closed 0.9 percent higher, while the Russell 2000 outperformed with gains of 2 percent.
As of the close Thursday, the three major U.S. stock indexes were up nearly 2 percent or more for the week so far. Traders also attributed some of the gains to short covering.
European stocks closed higher, with the German DAX up more than 1.5 percent for its first five-day win streak since late May. The STOXX Europe 600 about 1.5 percent higher.
The STOXX 600 Europe Banks index gained more than 2.5 percent for its first five-day win streak since April. The index is tracking for its best week since late 2011.
In Asia, the Nikkei 225 closed more than 1 percent higher while the Shanghai composite closed about half a percent lower.
U.S. stocks closed lower Wednesday, as declines in energy stocks weighed, and investors remained on edge ahead of the Brexit vote after a poll indicated a slight edge for leave over remain. Separate polls released after the close indicated more support for remain.
"Since we had a fairly low conviction as to how the vote would go, we were reluctant to make a bet in a general direction," said Mark Luschini, chief investment strategist at Janney Montgomery Scott.