Millions began voting Thursday in the United Kingdom on a bitterly-fought, knife-edge referendum that could tear up the island nation's EU membership and spark the greatest emergency of the bloc's 60-year history.
Above: Pensioners are ushered into a polling station to cast their ballot papers at the Royal Hospital in Chelsea, London on June 23, 2016.
Olivia Sudjic holds up a placard in favor of the "Remain" camp by a polling station in London on June 23.
A man leaves after voting at a polling station in Biggin Hill, England.
Britain's Prime Minister David Cameron and his wife Samantha leave after voting at a polling station in London.
Nigel Farage, the leader of the United Kingdom Independence Party (UKIP), has a coffee in The Old Jail pub, after voting in the EU referendum in Biggin Hill.
A "Leave" poster hangs in a window in London's Chelsea neighborhood.
People wait in line to cast their ballots at a polling station in the British overseas territory of Gibraltar, historically claimed by Spain.
The territory is staunchly in favor of staying in the EU.
A woman is reflected in a puddle of rain water as she arrives at a polling station at the Royal Hospital in Chelsea, London.
Scotland's First Minister Nicola Sturgeon leaves after voting in the EU referendum at Broomhouse Community Hall in Glasgow, Scotland, on June 23.