BRATISLAVA (Reuters) - Slovak police have charged a man with ordering the murder of investigative journalist Jan Kuciak and his fiancee, prosecutors said on Thursday, a case that triggered mass protests and the resignation of a prime minister.

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Special prosecutors named the suspect only as Marian K. during a televised news conference that marked a major step forward in the case that rocked the central European state.

Newspapers Hospodarske Noviny and Dennik N, without citing sources, identified the man as politically connected businessman Marian Kocner, who had been a subject of Kuciak’s reporting.

Kocner has previously denied having anything to do with the 27-year-old Kuciak’s killing. A few months before, Kuciak told police that Kocner had threatened to start collecting information on him and his family. Police pressed no charges.

Prosecutors, who could not be identified and whose faces were hidden from television cameras, did not confirm the two newspapers’ information nor deny it during the news conference.

A lawyer for Kocner, who is in custody on unrelated charges of forgery, did not reply to calls or text messages seeking comment.

Police arrested four other people in September, including a woman identified only by her initials AZ, who was also charged with ordering Kuciak’s killing. Media have identified her as Alena Zsuzsova. She has denied any wrongdoing.

One of the suspects has cooperated with investigators but his testimony was not the only thing that led to Thursday’s charges, prosecutors said on Thursday.

“The motive for the murder was Kuciak’s work as a journalist. The investigator (has based the charge) on objective evidence that can’t be specified at the moment,” one said.

Zsuzsova was never a target of Kuciak’s reportage but Slovak media have reported that she had business ties to Kocner.

Kuciak reported on fraud cases involving politically connected businessmen before he was found shot dead at home with his fiancee in February 2018.

The murders stoked public anger over perceived corruption in Slovakia, a country of 5.4 million people, leading to the biggest protests since communism ended three decades earlier.

Amid that unrest, Robert Fico resigned as prime minister, a post he had held for 10 of the previous 12 years. His government has stayed in power but the ruling party has weakened in polls.