A stunned European Union vowed to remain united on Friday despite Britain voting to leave, as fears grew that a "chain reaction" of further referendums could tear the bloc apart.

As Brussels, Paris and Berlin woke up to the grim news, leaders warned of a difficult divorce in a sign that Britain will win few concessions in negotiating life outside the circle of the other 27 members of the bloc.

Britons decided by 52 percent to 48 percent in favour of quitting the EU, a margin of more than one million votes, final results showed.

READ: Shocked EU vows unity after Brexit vote

Here is an infographic on how Britain voted to leave the European Union.

Political map following the vote in Britain's referendum on membership of the European Union.