The Commission said it would probe a suspected breach of the Digital Services Act (DSA), a set of EU rules that aims to tackle illegal content, transparency issues in advertising and disinformation.

Călin Georgescu, a hard-right critic of NATO who has praised Russia, secured a shock win in the first round of the Romanian presidential vote last month after running a TikTok-driven campaign. He had been polling in single digits before the vote.

But Romania’s Constitutional Tribunal later annulled the election owing to allegations of Russian meddling, in an act unprecedented in the country’s modern history. A new election will take place next year.

European Commission President Ursula von der Leyen said in a statement issued on Tuesday: “We must protect our democracies from any kind of foreign interference. Whenever we suspect such interference, especially during elections, we have to act swiftly and firmly.”

She added: “Following serious indications that foreign actors interfered in the Romanian presidential elections by using TikTok, we are now thoroughly investigating whether TikTok has violated the Digital Services Act by failing to tackle such risks.”

The Commission said its investigation would take into account information from declassified intelligence reports by the Romanian authorities.

It added that it would focus on TikTok's recommender systems and on risks linked to the “coordinated inauthentic manipulation or automated exploitation” of the service.

TikTok's policies on political advertisements and paid-for political content would also be scrutinized, the Commission said.