Romania's Iohannis will face the Social Democrat leader Dancila in a runoff on November 24.
Incumbent President Klaus Iohannis won the first round of the Romanian presidential elections held on Sunday.
Exit polls showed him as a clear winner, with Social Democrat leader Viorica Dancila in second place.
An exit poll conducted by IRES pollster showed Iohannis received 38.7% of the vote followed by Dancila with 22%. Save Romania Union head Dan Barna got 16.1%. Another poll by Curs-Avangarde ranked Iohannis first with 39% and Dancila with 22.5%.
Data by the electoral bureau, which is expected to unveil partial official results from Monday morning, showed a robust turnout of 48% with a record high diaspora voter presence of 660,000 - which was not taken into account by the exit polls.
Iohannis, who pledged to rekindle anti-graft efforts in one of Europe’s most corrupt nations, will face Dancila in the runoff of the presidential race on November 24.
Early turnout figures showed an important rise of the Romanian diaspora vote, which jumped from 161,262 in 2014 to over 660,000 in 2019. Voters were voting abroad in 835 polling stations around the world.
Romania's president nominates a prime minister, who has executive powers, after holding consultations with political parties. The president can also veto laws adopted by parliament by challenging them in the constitutional court or by sending them back to be re-considered.
Iohannis is trailed in the polls by Viorica Dancila, leader of the Social Democrats' (PSD) and a former premier, and by Dan Barna, head of the centre-right opposition Save Romania Union. Both are vying for a spot in the runoff with about 20% in opinion polls.
Romania has been monitored by Brussels over progress on reform of its judiciary since 2007. But, a succession of PSD governments have tried to roll back certain anti-corruption rules in recent years, joining the ranks of other ex-communist states in the European Union in incurring criticism over the rule of law.
In May, Liviu Dragnea, a former PSD leader, was sentenced to three and a half years in prison after being found guilty of graft.
In October the European Commission reported that backtracking from judicial reform and the fight against corruption persisted.
Iohannis, who won his first term as president in 2014, had challenged a contested overhaul of the judiciary and attempts to limit magistrates' independence.
He also spearheaded a national referendum where an overwhelming majority of Romanians said they wanted the government to be banned from altering legislation via emergency decrees, and advocated a national ban on granting amnesties and pardons for graft-related crimes.
If re-elected, Iohannis will have a chance to install chief prosecutors who say they are committed to tackling endemic corruption, supported by the liberal minority government of Prime Minister Ludovic Orban, an ally who won a parliamentary vote of confidence this month.
Observers said a win for Iohannis might bolster the Liberal Party's chance of forming a coalition government after a general election due in 2020 and restore investor confidence eroded by several years of political instability and fiscal largesse.
The country has 18.2 million eligible voters.
Polls opened at 0600 (0500 CET) on Sunday morning and closed at 2000 local time (19.00 CET).