A centre-right anti-graft party is on course to form Slovakia's next government after voters ousted the governing leftists in polls marked by backlash over a journalist's killing in the eurozone state.

Vowing to push through anti-corruption measures in the judiciary and police, the leader of the winning OLaNO party Igor Matovic managed to galvanise voter outrage over the murder of journalist Jan Kuciak and his fiancee and the high-level graft their deaths exposed.

The murder of a journalist has upended Slovakian politics, prompting many to attend a memorial on the second anniversary of his death last week The murder of a journalist has upended Slovakian politics, prompting many to attend a memorial on the second anniversary of his death last week Photo: AFP / VLADIMIR SIMICEK

The killings -- allegedly a hit ordered by a businessman with connections to politicians -- triggered the largest anti-government protests since communist times and led to the toppling of the powerful head of the populist-left Smer-Social Democracy (Smer-SD) Robert Fico as prime minister in 2018.

Fico's party colleague Peter Pellegrini took over as premier, but he conceded defeat overnight, congratulating Matovic on his stunning victory in Saturday's vote.

"People want us to clean up Slovakia. They want us to make Slovakia a fair country where laws will apply to everyone," Matovic told reporters in a speech overnight as the election results showed his party skyrocketing to victory, more than quadrupling its seats in the process.

(L-R) Igor Matovic, leader of anti-graft political movement OLaNO, his daughter Rebeka and his wife Pavlina (R) vote in Slovakia's parliamentary election. The murder of a journalist who exposed high-level corruption has fueled desire for change. (L-R) Igor Matovic, leader of anti-graft political movement OLaNO, his daughter Rebeka and his wife Pavlina (R) vote in Slovakia's parliamentary election. The murder of a journalist who exposed high-level corruption has fueled desire for change. Photo: AFP / VLADIMIR SIMICEK

"It was the death of Jan Kuciak and Martina Kusnirova that woke up Slovakia," he said, vowing that his administration will have "zero tolerance for corruption".

Slovakia's Prime Minister and election leader of the populist-left Smer-Social Democracy (Smer-SD) party, Peter Pellegrini votes in the parliamentary election. Slovakia's Prime Minister and election leader of the populist-left Smer-Social Democracy (Smer-SD) party, Peter Pellegrini votes in the parliamentary election. Photo: AFP / JOE KLAMAR

But according to Bratislava-based political analyst Juraj Marusiak, the centre-right OLaNO's win should not be seen as an outright rejection of populist politics.

He characterised Smer-SD's ousting as a "victory of right-wing conservative populism" reminiscent of the rise of right-wing populist parties in neighbouring EU countries.

"In this respect, the situation in Slovakia resembles that of its neighbours, Hungary or Poland or the Czech Republic," he added, while characterising OLaNO as more a "heterogeneous, protest-type party" than other governing right-wing parties in the region.

OLaNO party leader Igor Matovic speaks to supporters on his way to a resounding election victory OLaNO party leader Igor Matovic speaks to supporters on his way to a resounding election victory Photo: AFP / JOE KLAMAR

Unlike some eurosceptic or pro-Russian populist parties, OLaNO staunchly supports Slovakian membership of EU and NATO.

OLaNO, led by Igor Matovic, took 25.8 percent of the vote ahead of a stinging 14.9 percent for the governing Smer-SD party OLaNO, led by Igor Matovic, took 25.8 percent of the vote ahead of a stinging 14.9 percent for the governing Smer-SD party Photo: AFP / JOE KLAMAR

OLaNO took 25.02 percent of the vote for 53 seats in the 150-member parliament, full election results showed, and is now expected to seek coalition partners to clinch a majority of 78 seats.

Matovic said he expected to open talks with all parties except the outgoing Smer-SD, which won 18.29 percent for 38 parliamentary seats, and the far-right Our Slovakia LSNS, which received 7.97 percent for 17 seats.

Matovic said he would seek talks with the We Are Family conservatives, who scored 8.24 percent and now have 17 seats, as well as the liberal Freedom and Solidarity (SaS) party and the fellow liberal "For the People" party of ex-president Andrej Kiska -- which have 13 and 12 seats respectively.

But on Sunday the party leader insisted he was "not sure" whether he would become PM, saying it "depends if we can agree" with coalition partners, adding that otherwise the president "has the power to decide.

President Zuzana Caputova, a liberal, said Sunday on Facebook that she would announce her "next steps" on Monday, while Matovic said earlier she had invited him to talks via telephone.

Under the constitution, there is no deadline for the formation of a government. The president is required to call the first session of the new parliament within 30 days after the official election results are published.

An eccentric self-made millionaire and former media boss, Matovic set up "Ordinary People and Independent Personalities -- OLaNO" a decade ago.

Analysts suggest that Matovic, a 46-year-old media-savvy but unpredictable politician, has a good shot at becoming premier if he manages to unify the splintered opposition.

"There is a chance that this new government will last until the end of its term," said Slovakia analyst Tomas Koziak, the Rector of the University of Political Sciences based in Kutna Hora, Czech Republic.

"These parties have been in opposition for a very long time, therefore their top politicians are thirsty for power. Power is the strongest glue," Koziak told AFP.

The murder of Kuciak and his fiancee became a lightning rod for public outrage at graft in public life.

The fallout helped propel Caputova, a liberal lawyer and anti-graft activist, out of nowhere to win last year's presidential race in the country of 5.4 million people.

The turnout for Saturday's vote was 65.80 percent, full results showed -- the highest in nearly two decades.