Polls have opened in Britain for a referendum on whether the country should quit the European Union bloc it joined 43 years ago.

More than 46 million people are registered to vote in Thursday's plebiscite, which asks: "Should the United Kingdom remain a member of the European Union or leave the European Union?"

Polls are open until 10 p.m. (2100GMT), with results due early Friday.

The referendum has exposed deep divisions over issues including sovereignty and national identity.

"Leave" campaigners claim that only a British exit can restore power to Parliament and control immigration. The "remain" campaign led by Prime Minister David Cameron argues that Britain is safer and richer inside the 28-nation EU.

Financial markets have been volatile ahead of the vote, as opinion polls suggested a tight race.