A day of political drama unfolded in Britain on Friday as voters elected to leave the European Union and the Prime Minister David Cameron announced his intention to resign.

The historic decision to leave the EU will have far-reaching repercussions both domestically and internationally, and immediately plunged the 28-member bloc into its worst crisis since it was founded.

Cameron's bombshell came shortly after 8 am London time, when he announced he would step down in three months' time to allow a new prime minister to be in place to handle the complex negotiations surrounding Britain's departure.

The new leader has two years in which to invoke the start of the exit process, and there have been suggestions that it might be delayed in order to negotiate the best departure terms.

What has not yet become clear is the future of Britain's relations with two of its major trading partners, China and the US.