A populist party that wants to stop military aid to Ukraine and is critical of the EU and NATO has won Slovakia's election, results have showed.

The Smer-SD party led by former prime minister Robert Fico scored 23.3 percent, beating the centrist Progressive Slovakia on 17 percent, with almost all votes counted.

Experts see Fico's party's rise to power signaling a radical change in Slovakia's foreign policy, resembling that of Hungarian Prime Minister Viktor Orban. 

The 59-year-old Fico has vowed that Slovakia will not send "a single round of ammunition" to Ukraine and has called for better relations with Russia.

For Fico to become prime minister, his party needs to secure 42 seats in the 150-member parliament and so will need coalition partners for a majority.

The leftwing Hlas-SD, which emerged in 2020 when a group of Smer lawmakers quit Fico's party, is one potential partner, with an expected 27 seats.

Fico and Pellegrini are expected to team up with the nationalist Slovak National Party (SNS), adding another 10 more seats to the coalition, for a parliamentary majority of 79 seats.

The SNS, which is also opposed to military aid for Ukraine, has twice in the past joined in coalitions with Fico.

Slovakia has been one of Europe's biggest donors to Ukraine since Russia launched its special military operation in Donbas in 2022.

Slovakia's Defense Minister Martin Sklenar had visited Kiev just ahead of the vote, and on election day Ukrainian President Vladimir Zelensky praised Slovakia for "standing with Ukraine".

Slovakia emerged as an independent country in 1993, following a peaceful split with the Czech Republic. In 2004, it joined both the EU and NATO.