Romania's beleaguered left-wing government risks collapse in a no-confidence vote Thursday, just weeks before a presidential election and amid controversy over the country's nominee for EU commissioner.

NATO will send units to Romania, alliance head Jens Stoltenberg said Tuesday, on top of battalions being deployed in the three Baltic states and Poland in response to Russia's intervention in Ukraine.

Romania's Social Democrats topped the polls in weekend municipal elections that were overshadowed by corruption scandals, with their candidate becoming the first female mayor of Bucharest, partial results showed Monday.

Gabriela Firea, a 43-year-old former journalist backed by a leftist alliance of the Social Democratic Party (PSD) and the National Union for the Progress of Romania, received 43.56 percent of the vote in the capital.

Four more people have died of injuries sustained in a devastating nightclub blaze in Romania, taking the toll in the inferno that brought down the government to 50, hospital sources said Wednesday.

Two of the four latest victims of the October 30 fire at a Bucharest club had been undergoing treatment in Britain, where they were transferred at the weekend.

Romania's president appealed for protesters' support on Sunday in reforming the country, as the death toll rose to 45 from a horrific nightclub fire that brought down the government.

Klaus Iohannis was met with shouted slogans and whistles from demonstrators seeking "profound change" as he paid a visit to the capital's University Square, the focal point of nearly a week of protests.

Romania's embattled Prime Minister Victor Ponta, mired in a corruption scandal, resigned Wednesday following a deadly nightclub blaze, a day after more than 20,000 people rallied in Bucharest to demand he step down.

The 43-year-old announced his resignation on television, saying it was right that top officials took responsibility for Friday's tragedy at the Colectiv disco in Bucharest, which left 32 dead and nearly 200 injured.

A Romanian court has launched a probe into former president Ion Iliescu for alleged crimes against humanity over the violent suppression of protests in 1990, months after the fall of the Communist regime, prosecutors said Wednesday.

"Mr. Iliescu has been informed that legal proceedings have been initiated against him," a spokesman for prosecutors told AFP.

Romania's embattled Prime Minister Victor Ponta survived a no-confidence vote on Tuesday, barely a week since the start of his trial on wide-ranging corruption charges.

The 43-year-old Social Democrat leader has faced relentless calls to stand down over the graft case, which is complicating government efforts to strike a new financial deal with the IMF and the EU.

European Union leaders, who will gather for an emergency summit on the migration crisis on Wednesday, are expected to give extra funding to Turkey, Jordan, Lebanon and U.N. agencies.

The leaders are hoping that the funding would help stop the flow of refugees to Europe.

Bulgaria began on Thursday deploying up to 1,000 troops to buttress its southeastern border with Turkey as hundreds of migrants remained stranded for a third day on the Turkish side, a senior official said.

"We have triggered a plan for the start of the step-by-step deployment of up to 1,000 troops along the whole Bulgarian-Turkish border (within the next week)," interior ministry chief of staff Georgy Kostov said.