Far-right, Moscow-friendly candidate Călin Georgescu dramatically won in the election's first round — shocking the country's political establishment.
Romania's Constitutional Court has requested the country's central election authority to recount and check ballots from Sunday's presidential election's first round.
The top court also decided to postpone until Friday a request to annul the election's results, a decision that means the two candidates cannot start their campaigns.
Relatively unknown, TikTok-famous far-right nationalist Călin Georgescu stunned Romania when he beat several well-established candidates on Sunday with 23% of the vote.
Georgescu was polling at just below 5% a day before the vote was held on Sunday but ended up topping the ballot.
He was set to face pro-EU liberal centre-right candidate Elena Lasconi in the runoff set for 8 December.
The court's decision comes after two candidates who lost in the first round, Christian Terheș and Sebastian Popescu, filed complaints.
Popescu, whose request was rejected, alleged Georgescu misled the electorate and received outside financial support for his hugely successful TikTok campaign.
Terheș said that the withdrawal of another candidate just before the election confused voters and could amount to election fraud, according to local media.
Georgescu hasn't commented directly on the complaints against him but said previously he had no campaign budget and was helped through volunteers.
The former sustainable development expert has been critical of Romania's NATO membership and suggested that Russian President Vladimir Putin is one of the world's remaining true leaders.
The candidate has also called for an end to the war in Ukraine and described two Romanian World War II Nazi collaborationist leaders as "heroes".
TikTok phenomenon
The 62-year-old built up a successful campaign through the Chinese-owned social media app TikTok, where he posts videos of him attending church, running, and speaking on podcasts.
Such was his success on the app that the deputy head of the country's telecoms regulator, ANCOM, has requested the suspension of TikTok in Romania from Thursday amid fears that his campaign was boosted through bots sharing his posts.
Georgescu's popularity exploded in recent weeks, gaining 52 million views days before the vote's first round.
Pavel Popescu, the vice-president of ANCOM, said he requested the app's suspension until "the completion of the investigation by the state institutions regarding the manipulation of the electoral process," according to Profit news site.
Romania's National Audiovisual Council has also asked the European Commission to open a formal probe into the role of the app in the elections.
TikTok has dismissed the allegations, arguing it enforces its community guidelines "aggressively."
Protests have erupted in Romania in response to Georgescu's victory, with thousands of young Romanians protesting against the result in Bucharest on Tuesday.
Lasconi said on Monday, "Let us be very clear, Calin Georgescu is an open admirer of Vladimir Putin. He is open against NATO and the European Union … He is for Romania’s isolation, which he calls neutrality ... And without NATO we are at the mercy of Russia.”
Georgescu has denied criticism lobbied against him that he is an extremist, saying, "We remain directly linked to European values, but we must find our (own) values," adding that he was not a "fascist".