Daniel Lipsic, a lawyer representing the families of Jan Kuciak and Martina Kusnirova, said suspects were arrested early on Thursday, with local media reporting one or more arrests.

The Slovak police said on its Facebook page it had detained "persons suspected of violent crime" and was carrying out "home searches," but did not say in which case.

Prime Minister Peter Pellegrini wrote on Facebook that "police have arrested the suspects in the murder of two innocent young people," adding that the ongoing investigation was "a priority" for his government.

Read more: Slovakia: After Jan Kuciak, killing journalists now 'within realm of possibility'

Slovaks celebrating the resignation of Prime Minister Robert Fico and his government in Bratislava in March

A contract killing?

Kuciak, who had written about political corruption in Slovakia, was found shot dead along with Kusnirova at their home outside Bratislava on February 21. Slovak authorities have said they believe it was a contract killing connected to Kuciak's work investigating possible widespread government corruption and ties between politicians and Italian gangsters.

The murder led to mass protests that forced the resignations of then-Prime Minister Robert Fico and Interior Minister Robert Kalinak as well as the head of the Slovak police, Tibor Gaspar.

Kuciak was investigating the alleged role of Italian crime syndicate 'Ndrangheta in siphoning off EU agricultural subsidies designated for Slovakia. He also uncovered links between Slovak officials, mainly from the ruling SMER party, and Italian families with connections to the Calabrian mafia. His colleagues published the results of his investigations after his death.

Slovak police have been accused of destroying evidence, lack of transparency and inappropriately investigating Kuciak's peers.

jbh/ng (AP, Reuters)

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