Incumbent Klaus Iohannis won the second round of Romanian presidential polls on Sunday, according to exit polls, a result that would confirm the pro-European trajectory of the eastern EU member state.

Thirty years after the fall of communism, the centre-right former physics professor won between 64.8 and 66.5 percent of the vote, exit polls showed, beating Social Democrats (PSD) leader and former prime minister Viorica Dancila.

Dancila received between 33.5 and 35.2 percent, the worst-ever result for the PSD, which has dominated Romanian politics since the fall of communism in 1989.

"I promise to be a president for all Romanians... A modern, European, normal Romania won today," a jubilant Iohannis said.

The 60-year-old from the German minority, who already staged a surprise win over the PSD in 2014, has campaigned to help build functioning institutions without corruption.

The election was fought against a background of deep resentment over controversial judicial reforms seen to benefit PSD politicians, which led to massive street protests and irked Brussels.

The PSD-led government collapsed in October in a no-confidence vote, capping months of political uncertainty under the left-wing party.

'Waiting for things to get better'

Stan Mihai, a 76-year-old pensioner who voted in the capital Bucharest, told AFP Sunday's vote was "a choice for the wellbeing of Romania".

"We're waiting for a revolution, for things to get better. But we are waiting for this, and nothing comes our way," he said. 

In the first round of voting on November 10, Iohannis won 38 percent of the vote, ahead of 13 other candidates. Dancila came second with 22 percent.

But voters who backed lower-placed candidates had been expected to largely swing behind Iohannis to give him another five-year term.

A total of 18.2 million Romanians were eligible to vote, including a record 650,000 voters abroad.

Part of a four-million strong diaspora who have emigrated in search for better paying jobs, they tend to favour liberal candidates.

The PSD government had engaged in a long battle with the European Union over allegations it was trying to push through the measures to neuter the judiciary. Iohannis backed Brussels in the dispute.

The left-wing party, which is seen as the successor of the ruling elite before the overthrow of communism, has been accused of widespread corruption.

And while nationalism has been less present in Romanian politics than elsewhere in the region -- such as in Hungary or Poland -- the PSD tried to frame its clashes with EU institutions as evidence that it was standing up for Romania.

- Judicial controversy -
After the PSD-led administration's fall, Iohannis tasked ally Ludovic Orban with forming a new government to be in place until legislative elections due late next year.

Former foreign minister Cristian Diaconescu said Iohannis -- who has made the rule of law a central plank of his campaign -- represents the "only European and Euro-Atlantic option".

Under the constitution, Romania's president is responsible for foreign affairs as well as approving the appointment of judges and top prosecutors.

Hundreds of thousands of Romanians have protested against the judicial reforms proposed by the PSD, seen as giving politicians a way to avoid corruption sentences.

"I'm very upset. They made rules just to help themselves," said Marin Cumatrenco, a 20-year-old film student who voted early Sunday in Bucharest. The most important for him was to "continue the European course", he added.

Sociologist Alin Teodorescu has estimated that introducing the reforms has cost the PSD more than a million votes.

'Dictator' vs 'toxic'

The PSD, which has become increasingly reliant on an ageing, rural electorate, has accused Iohannis of being a "dictator".

Criticised for refusing any face-to-face debate during the campaign, Iohannis, in turn, called his rival the "incarnation of a toxic regime".

Dancila, 55, an engineer by training, has highlighted the strong economic growth recorded during the PSD's time in office, including increases in pensions and public sector salaries.

But this largesse has sparked concerns by the European Union and the International Monetary Fund (IMF), which has warned about the country's rising fiscal deficit.

In May, the PSD's former chief and strongman, Liviu Dragnea was jailed on corruption charges, and the party also saw its support plunge during European elections.