One week ahead of a decisive general election, thousands of Slovaks rallied nationwide on Friday marking two years since the gangland-style murder of a journalist upended politics in the EU country hounded by corruption.

Jan Kuciak and his fiancee Martina Kusnirova were gunned down at their home on February 21, 2018, in a hit allegedly ordered by Marian Kocner, a wealthy businessman with ties to senior politicians who is now on trial for the crime.

The 28-year-old investigative journalist had written several articles revealing Kocner's shady business activities.

More than ten thousand people, some holding flickering candles, rallied in over 50 cities and towns across Slovakia on Friday evening in memory of the young couple.

The double murder sparked mass protests that forced then populist prime minister Robert Fico to quit and propelled lawyer and anti-graft activist Zuzana Caputova to win last year's presidential race.

Highlighting public outrage over high-level corruption, Kuciak's murder looms large over next Saturday's fragmented vote.

Candles were lit spellng out the love between, and for, Jan Kuciak and his fiancee Martina Kusnirova who were gunned down two years ago
Candles were lit spellng out the love between, and for, Jan Kuciak and his fiancee Martina Kusnirova who were gunned down two years ago AFP / JOE KLAMAR

Around 8,000 people gathered in a central square in the capital Bratislava, where a blanket of candles lit up the ground at an ad hoc memorial.

Kuciak's father called the election "crucial", speaking to AFP at the rally.

"It is very important what kind of people will get into power," said Jozef Kuciak.

"I've come because I believe it's still important to fight for democracy and freedom in Slovakia," Bratislava university student Lubos Janak told AFP at the protest, adding that he had "felt gloom and a lack of freedom" following the murders.

"I believe that the election results will reflect what happened two years ago," he added.

Kuciak's parents Jozef and Jana Kuciak address the memorial crowd on Friday
Kuciak's parents Jozef and Jana Kuciak address the memorial crowd on Friday AFP / JOE KLAMAR

Hit hard by the fallout of the double murder, opinion polls show that support is waning for Fico's governing left Smer-Social Democracy (Smer-SD) party while its current coalition partners could fall out of parliament altogether.

Capitalising on its anti-establishment posture, surveys show the far-right Our Slovakia LSNS is on track to capture more seats.

Polls also suggest that a gaggle of opposition centre-right, liberal and progressive parties campaigning on promises to root out graft have a good shot at forming a government if they can set aside their differences.

President Caputova brought two red roses to the house of the murdered couple earlier on Friday.

"If the murderers thought death would discourage other journalists from exposing high profile (corruption) cases, they were mistaken," Caputova wrote on her official Facebook page.

"What Jan Kuciak did not finish, others will," she said.

Attending the Friday rally in Bratislava, Igor Matovic, head of the surging opposition OLaNO centre-right anti-graft party, told AFP that the double murder had "opened up the eyes of those who didn't want to see how corruption is devastating our society."

Surveys suggest Matovic stands a real chance of becoming prime minister should he manage to unify a splintered opposition.

"The murders changed the political scene, new parties emerged and immediately gained support," political analyst Grigorij Meseznikov told AFP, adding that the election would "probably bring the creation of a centre-right, pro-democracy-oriented ruling coalition."

But according to Smer-SD leader Robert Fico, the Kuciak murder was "abused for political purposes.

"If it wasn't for the murder, I'd stand here in front of you as a prime minister with 30 percent support," he told journalists in Bratislava on Friday.