Romania's central election authority on Sunday barred far-right pro-Russian candidate Calin Georgescu from running in May's presidential election re-run.
The rejection of his candidacy, which was condemned by far-right party leaders as undemocratic, can be challenged at the constitutional court.
Dozens of supporters of the populist Georgescu gathered outside the election bureau shouting "Freedom" and briefly tried to force their way through the security cordon.
Georgescu submitted his candidacy for the May ballot re-run on Friday amid doubts that he would be allowed to run.
Romania's highest court annulled the ballot two days before the second round of voting in December, citing allegations of Russian interference in Georgescu's favour, which Moscow has denied.
Tech billionaire and Trump adviser Elon Musk called the election authority's decision "crazy" on his social media platform X.
Georgescu is under criminal investigation on six counts, including membership in a fascist organisation and communicating false information about campaign financing. He has denied all wrongdoing.
