Provincial mayor Klaus Iohannis defied expectations to win Romania's presidential election on Sunday, Nov 16, inflicting a shock defeat on Prime Minister Victor Ponta that was cheered by thousands of anti-government protesters on the streets, Reuters reported.

An ethnic German whose campaign was backed by two center-right parties, Iohannis turned round a 10-point deficit to win the runoff, as widespread anger at voting problems overseas appeared to galvanize the anti-Ponta camp.

Analysts had said that victory for Ponta might have helped make Romania a more stable nation, with the main levers of power held by one bloc. By contrast, Iohannis's win could trigger renewed political tensions in one of Europe's poorest states.

Backed by a well-oiled party machine, Ponta had led opinion polls throughout the campaign and comfortably beat Iohannis in the first round election on Nov 2.

But Ponta abruptly conceded defeat after the exit polls were released. Later the first official results showed Iohannis on 55.8 percent against 44.2 percent for Ponta, with a third of polling stations counted. Turnout was at its highest since 1996.

Despite the loss, Ponta ruled out quitting as prime minister and said his Social Democrat alliance would remain in power until parliamentary elections due in 2016.

Thousands of people took to the streets of Bucharest and other cities to voice their anger at Ponta's government on Sunday night and demand his resignation.