Italian prosecutors warned Slovakian authorities about "dangerous" infiltration by a powerful Italian organised crime syndicate even before a reporter was shot dead, according to a top anti-mafia fighter.
Franco Roberti, who recently retired as Italy's national anti-mafia prosecutor, said of the 'ndrangheta syndicate's expansion into Slovakia: "We warned authorities in Bratislava, but unfortunately they didn't heed us."
On Thursday, Slovakian police raided houses linked to the alleged members of the syndicate in connection with the fatal shooting of investigative journalist Jan Kuciak and his girlfriend.
Seven men were detained as suspects in the raids in the eastern towns of Michalovce and Trebisov, national police chief Tibor Gaspar said.
The bodies of 27-year-old Mr Kuciak and his girlfriend, Martina Kusnirova, were found on Sunday in their house in Velka Maca, east of the capital, Bratislava. They had both been shot. Mr Kuciak's last, unfinished story had been about the activities of the Italian 'ndrangheta in Slovakia.
Mr Roberti said the 'ndrangheta might have killed Mr Kuciak because "there was no other way to silence him".
He added the "corruption" of local officials plays a big role in the 'ndrangheta's activities abroad.
One of those detained on Thursday was Antonino Vadala, an Italian who conducted business with at least two officials close to Slovakian prime minister Robert Fico. Those two officials resigned on Wednesday.
Scotland Yard, the FBI, Czech and Italian police and Europol are helping Slovakian authorities investigate the killings.
Some 25 marches were planned on Friday in Slovakia to honour the murdered couple, including one in the capital, Bratislava, which President Andrej Kiska will attend.
Other commemorative gatherings are planned in two dozen cities abroad, including London, Paris and Brussels.
Also on Friday, the secretary general of Reporters Without Borders called on Mr Fico to apologise for insulting journalists. Christophe Deloire deplored what he called the "appalling climate for journalists" created by government leaders in Hungary, Poland, the Czech Republic and Slovakia.
Mr Fico is known for his numerous attacks on the media.
Meeting Mr Fico in Bratislava, Mr Deloire said he took note of the government efforts to investigate the killings.
"(But) we nonetheless think you should express regret and apologise for having insulted journalists on several occasions," Mr Deloire said.