Romania's ruling leftist Social Democrats (PSD) looked set to win the most votes in a parliamentary election on Sunday, fending off a resurgent far-right movement that challenged the country's pro-Western orientation, partial results showed.

The vote is the second of three consecutive ballots for both a new parliament and a new president, after the first round of the presidential election on November 24 saw an independent far-right candidate, Calin Georgescu, emerge from relative obscurity to become the frontrunner.

His unexpected win ushered in support for ultra-nationalist, hard-right parties, some with overt pro-Russian sympathies, which political analysts said could undermine Romania's support for Ukraine.

If final results confirm the preliminary count, a pro-Western coalition led by the PSD would likely have enough seats in parliament to form a government, although the far right would be a substantial force in the legislature.

However, a broad coalition would be difficult to form amid disagreements over reforms and measures needed to rein in the country's gaping budget deficit, now the highest in the EU at eight percent of economic output.

After a campaign dominated by voters' concerns over budget problems and the cost of living, the election pitted the far-right contenders against pro-European mainstream parties that have angered their voters with infighting and corruption allegations.

Far-right parties have also used Romania's championing of Ukraine to stoke fears the war could spill over the border unless the country halts its support, as well as resentment over alleged preferential treatment for refugees from Ukraine.

Romania has the EU's biggest share of the population at risk of poverty, and swathes of the country need investment to attract jobs. (Reuters)