Greek Prime Minister Alexis Tsipras is seen on a television monitor as he addresses the nation in Athens, Greece, July 5, 2015. [Photo/Agencies]

ATHENS, Greece - Greece lurched into uncharted territory and an uncertain future in Europe's common currency Sunday after voters overwhelmingly rejected demands by international creditors for more austerity measures in exchange for a bailout of its bankrupt economy.

Results showed about 61 percent voted "no," compared with 39 percent for "yes," with 100 percent of the vote counted. The referendum - Greece's first in more than four decades - came amid severe restrictions on financial transactions in the country, imposed last week to stem a bank run that accelerated after the vote was called.

Thousands of jubilant government supporters celebrated in Syntagma Square in front of Parliament, waving Greek flags and chanting "No, no, no!"

Early trading on Asian markets indicated investors were alarmed, as stock indexes fell.

It was a decisive victory for Prime Minister Alexis Tsipras, who had gambled the future of his 5-month-old coalition government - and his country - in an all-or-nothing game of brinkmanship with Greece's creditors from other European countries that use the euro currency, the International Monetary Fund and the European Central Bank.

"Today we celebrate the victory of democracy," Tsipras said in a televised address to the nation, describing Sunday as "a bright day in the history of Europe."

"We proved even in the most difficult circumstances that democracy won't be blackmailed," he said.

Tsipras called the referendum last weekend, saying a "no" vote would strengthen his hand to negotiate a better deal for his country. His government has said it believes it would be possible to conclude a deal with creditors within 48 hours.