The “Leave” side garnered 51.9 percent of the vote, while the “Remain” side garnered 48.1 percent, according to the commission. The financial markets reacted quickly to the results: Around 8 a.m. local time, the British stock market had plunged 7.7 percent and the German index had fallen 10 percent, according to The Associated Press.
Shortly after 6:30 a.m. local time (1:30 a.m. ET), the winning side became apparent, when the Leave side had more than 17 million votes, exceeding the 16.8 million needed to win, which is more than 50 percent of the vote.
Jenny Watson, chairwoman of the United Kingdom Electoral Commission, soon after officially declared that the U.K. had voted to exit the European Union. Voter turnout, at 72.2 percent, was high for the U.K.
Nigel Farage, leader of the U.K. Independence Party, a proponent of the Leave movement, tweeted, "We've got our country back. Thanks to all of you. #IndependenceDay."
Farage also tweeted a video to his supporters in which he said, "We've done it. We've overturned the establishment, the big banks, the big businesses."
Farage was also quick to make the TV interview rounds, kicking off his morning with an appearance on "Good Morning Britain," on which he said, "I almost didn't dare to dream it would happen."
London's former Mayor Boris Johnson, who campaigned for the U.K. to leave the European Union, was booed as he left his London home after the results were announced.
The European Central Bank released a statement saying it was "closely monitoring financial markets" and would be ready to provide additional liquidity, if needed, in euro and foreign currencies.
Mark Carney, the Bank of England's governor, also made a statement after the results.
"Some market and economic volatility can be expected as this process unfolds. But we are well prepared for this," Carney said, adding that the bank is ready to provide more than £250bn [about $347 billion] of additional funds to the financial system through normal market operations.
England and Wales supported Leave, while Scotland and Northern Ireland voted Remain. more than 1.6 million Scottish votes backed Remain against 1 million for Leave. More than 440,000 Northern Irish voters supported Remain and about 349,000 backed Leave.
England supported Leave by nearly 15 million votes against Remain's 13 million. London, including West Oxfordshire, home to Prime Minister David Cameron’s Witney constituency, supported Remain.
European Union officials in Brussels are trying to figure out the next steps after the U.K.'s dramatic decision. Jean-Claude Juncker, the European Commission president, is hosting meetings today with the leaders of the European Council and Parliament, and Dutch Prime Minister Mark Rutte, whose country holds the E.U.'s rotating presidency. They will attempt to agree on how to handle the vote, which will lead to a member country’s leaving the E.U. for the first time in history.
Donald Tusk, president of the European Council, tweeted his reaction, writing, "We are prepared for this negative scenario. There will be no legal vacuum."
He also tweeted a video of his news conference:
The first results from England today showed greater than expected support for leaving. Newcastle, which was the first to declare a result in the country, voted to remain in the E.U. but by a very small margin: 50.7 percent voted to stay while 49.3 percent voted to leave. Sunderland voted to leave at 61.3 percent while 38.7 percent voted to stay.
An online petition on the U.K. Parliament’s petition website asking lawmakers to reconsider the referendum outcome reached more than 72,000 signatures hours after the results were announced.
After news of the Leave side's victory, a White House official released a brief statement: "The president has been briefed on the incoming returns in the UK referendum, and he will continue to be updated by his team as the situation warrants.
“We expect the President will have an opportunity to speak to Prime Minister Cameron over the course of the next day, and we will release further comment as soon as appropriate."