By George Georgiopoulos and Michele Kambas ATHENS (Reuters) - Greeks voted on Sunday in a referendum that could determine their future in Europe's common currency, with banks shuttered, the treasury empty and a population desperate, angry and so deeply split that the outcome was too close to call. The referendum is officially a Yes or No vote on a bailout offer from creditors, but a 'Yes' could bring down the government of Prime Minister Alexis Tsipras, while European leaders say a 'No' could force a chaotic exit from the euro. The country of 11 million people is being asked whether to accept the offer which left-wing leader Tsipras rejected eight days ago.