Demonstrations calling for justice for a murdered journalist continue in Slovakia after police announced the released of seven suspects in the killing of Jan Kuciak, who was investigating alleged corruption.

Kuciak, 27, was reportedly writing a piece about alleged links between Slovak politicians and Italian organised crime.

He and his fiancee, Martina Kursnirova, were both shot and killed in their home last Sunday.

He was laid to rest in Stiavnik on Saturday, near the border between Slovakia and the Czech Republic.

The seven suspects were detained by police on Thursday were named by Kuciak in his report.

They were released on Saturday after no evidence was found in a 48-hour window during which the evidence can be attained.

Kuciak's research reportedly found that Italian businessmen with ties to the Ndrangheta, Italy's most powerful organised crime syndicate, were operating in Eastern Slovakia.

The businessmen were allegedly embezzling EU funds for the region, which borders Ukraine.

Antonio Vadala, one of the businessmen named by Kuciak, was among the suspects released by Slovak police.

Robert Fico, Slovak prime minister, reportedly has business ties with some of the Italians suspected of links to organised crime.

Continued protests

Slovakia saw protests in 25 cities on Friday, including the capital, Bratislava.

Roughly 20,000 Slovaks marched to the government headquarters in Bratislava, where they shook the gates of the building and chanted "Enough of Fico". The protesters were led by President Andrej Kiska.

Demonstrators held posters with slogans like "An attack on journalists is an attack on all of us".

Fico has offered one million euros (roughly $1.2m) for anyone who can give investigators information about the case.

The prime minister has a contentious history with journalists. He previously referred to reporters as "slimy snakes" that are "anti-Slovak".

Kuciak's murder was the first killing of a journalist in Slovakia's history. He and Kursnirova were due to be married in May.

His investigation into ties between Slovak politicians and organised crime was released posthumously.