Four opinion polls published on Friday had the 'Yes' vote marginally ahead; a fifth put the 'No' camp 0.5 percent in front, but all were well within the margin of error.
Many analysts believe the last-minute change in the public mood was prompted by a major pro-government and anti-austerity rally held in front of the Greek Parliament on Syntagma Square, where Prime Minister Alexis Tsipras, elected in January on a promise to end years of austerity, urged an estimated 60,000 supporters packing the downtown square to spurn the tough terms of an aid deal offered by international creditors.
Alexis Tsipras rejected EU leaders' warnings that a ‘No’ result in Sunday's referendum on whether to accept the bailout could see Greece forced to leave the Eurozone.
"On Sunday, we are not simply deciding to remain in Europe — we are deciding to live with dignity in Europe," he said.
Approximately 10 million Greek citizens aged 18 and over will cast their votes until 7:00pm local time (1600 GMT) Sunday to decide whether to accept austerity measures proposed by creditors with a ‘yes’ or ‘no’ to euro currency referendum expected from 1800 GMT.