A party headed by a pro-Kremlin figure came out top after securing more votes than expected in an election in Slovakia, preliminary results show, in what could pose a challenge to NATO and EU unity on Ukraine.

According to preliminary results released by Slovakia’s Statistical Office at 9 a.m. local time, Robert Fico’s populist SMER party won 22.9% of the vote.

Progressive Slovakia (PS), a liberal and pro-Ukrainian party won 17.9%.

Fico, a two-time former prime minister, now has a chance to regain the job but must first seek coalition partners as his party did not secure a big enough share of the vote to govern on its own.