A George Simion victory could isolate Romania, erode private investment and destabilise NATO's eastern flank, where Ukraine is fighting a three-year-old Russian invasion, political observers say.

Romania's previous presidential election was cancelled over allegations of campaign fraud and Russian interference.

He is banned from entering Ukraine, which he claims mistreats its small Romanian minority, and Moldova, where he wants a referendum on unification with Romania to be held (Romanian is the main language spoken in Moldova,