A small far-right party in Romania has thrown its weight behind Prime Minister Victor Ponta, who on the weekend won the first round in elections to become president, a ruling coalition leader said Tuesday.

UNPR, a member of Ponta's leftist coalition, signed a cooperation agreement with the far-right Romania Mare (PRM), a party official said.

Romania's Prime Minister Victor Ponta led the first round of the presidential election according to near-complete results on Monday, but he was pushed harder than expected by his conservative rival.

The European Union is watching the election closely because of fears that Ponta could reverse reforms aimed at tackling rampant corruption in one of the bloc's poorest countries.

Romanian Prime Minister Victor Ponta, now tipped for the presidency, is an ambitious, confrontational politician who has risen rapidly in the post-communist era.

Polls suggest the 42-year-old boyish-looking prime minister should easily win the first round of presidential elections on Sunday, and go on to beat centre-right leader Klaus Iohannis in the second round on November 16.

The former chief of a notoriously brutal communist-era prison camp in Romania went on trial Wednesday for alleged crimes against humanity.

It was the first such attempt since the fall of communism nearly a quarter century ago to bring to justice anyone from the leadership of a prison system that locked up 600,000 dissidents between 1947 and 1989.

Romania's former prime minister Adrian Nastase, sentenced to four-and-a-half years in jail for his role in two corruption cases, was released from prison on Thursday. 

Romania is to try a former Communist-era labor camp chief for crimes against humanity over the deaths of 103 political prisoners half a century ago, prosecutors said Monday.

Ioan Ficior is accused of persecuting "political prisoners from the camp of Periprava" (south-east) by subjecting them to "treatment aimed at their physical destruction", the Romanian prosecutor's office said in a statement.

Flooding caused by torrential rains in eastern Europe has killed three people, with a further four missing, Romanian and Bulgarian authorities said Wednesday.

In Arges in southern Romania -- one of the worst hit areas -- a 72-year-old man was swept away by floodwaters as high as two meters (six and a half feet), local authorities said.

One of Romania's deputy prime ministers resigned from the government on Friday in a dispute over an international initiative calling for better the protection of minorities in the EU.

Kelemen Hunor, who was also culture minister and remains a member of Romania's Hungarian minority party, had railed against a government decision to oppose the drive by the Federal Union of European Nationalities, a non-governmental organisation, calling for the safeguarding of basic rights for minorities across the continent.

Romania's president Traian Basescu on Monday vowed to stay on for his full term in office, rejecting calls to stand down after his brother was arrested for accepting bribes from a mobster.

"I will pursue my term to the last day," Basescu told a press conference.

Around a thousand tourists from Romania have been left stranded by flash floods in Bulgaria which left 14 dead around the Black Sea resort of Varna, the Romanian government said on Saturday.

Most of the Romanians affected were in the seaside town of Albena, near Varna.