BRATISLAVA, Slovakia (AP) — An investigative journalist shot dead in Slovakia last week was working on a story about the activities of Italian mafia in his country and their links to people close to Prime Minister Robert Fico.

Jan Kuciak's Aktuality.sk news website published his last, unfinished story on Wednesday. It describes the activities of members of the Italian 'Ndrangheta criminal group in eastern Slovakia, and the business ties of one of them with a senior assistant to Fico and another official close to him.

The bodies of 27-year-old Kuciak and his girlfriend, Martina Kusnirova, were found Sunday evening in their house in Velka Maca, east of the capital, Bratislava. Kuciak is the first journalist killed in Slovakia.

In his story he described, among other details, the activities in agriculture, real estate and other sectors of a Slovak-based Italian man believed to belong to the criminal group.

He also detailed the man's business ties to Maria Troskova, a former model who is now the chief state adviser at the government office, and Viliam Jasan, who currently serves as the secretary of Slovakia's security council, a body that deals with key security issues.

After the first details of the story appeared in Aktuality.sk and a newspaper, Sme, on Tuesday, Fico dismissed the reports.

"You link innocent people to a double murder without any evidence," Fico said. "Don't do it."

The opposition was not impressed and called on national police force President Tibor Gaspar and Interior Minister Robert Kalinak to resign. It was planning a protest rally in Bratislava for later Wednesday.

The killings claimed their first political victim on Wednesday when Culture Minister Marek Madaric announced he was resigning from his government post.

A member of Fico's leftist Smer-Social Democracy party, Madaric said it was his personal decision.

"As the culture minister, I am not able to cope with the fact that a journalist was killed during my time in office," he said.

Also Wednesday, Justice Minister Lucia Zitnanska, from a junior coalition partner of Fico's Smer, said it was "absolutely unacceptable" that anyone with ties to organized crime would be working at the government office.

Students plan marches to honor Kuciak in a number of Slovak cities on Friday.

Aktuality.sk said Kuciak cooperated on the story with the Czech Centre for Investigative Journalism, the Investigative Reporting Project Italy and the international Organized Crime and Corruption Reporting Project.

The Czech center said it had been working with Kuciak for more than 18 months.