A police statement said the seven suspects were released because no evidence had emerged during the 48 hours they can be legally detained.
Leading the funeral mass, Bratislava Archbishop Stanislav Zvolensky told mourners that "if the murderer thought he was able to silence Jan, he was wrong".
Police in Slovakia have released seven Italians who were detained as suspects in the killing of an investigative journalist and his girlfriend.
Jan Kuciak, who was writing an article on corruption allegations, and his fiancée Martina Kusnirova were shot dead at their home last Sunday.
Kuciak's last, unfinished story was about the activities of Italian mafia in eastern Slovakia and their ties to people close to Prime Minister Robert Fico.
"During the legal timeframe - 48 hours - (police) checked and searched for facts needed for an indictment".
The murders shocked the country and led to protest marches in 25 cities.
The journalist was investigating alleged political corruption linked to Italian organized crime in Slovakia. The distrust is strong as people believe politicians are abusing their power to amass personal fortunes.
The murder prompted demands from Fico's coalition partners for the resignation of senior officials.
The FBI, Scotland Yard and Europol are helping Slovak police with the investigation.
His last, unfinished article was published posthumously by Slovak and worldwide media.
The ultranationalist Slovak National Party is the third member of the coalition.
"(But) we nonetheless think you should express regret and apologise for having insulted journalists on several occasions", Mr Deloire said.
But contacted by AFP, Harlem Desir, the Freedom of the Media representative at the Organisation for Security and Co-operation in Europe, confirmed that Deloire had called on Fico to apologise to journalists.