Police were still checking the alibi of the individual, identified as "a Romanian citizen of Ukrainian descent", and he was not formally declared a suspect, Atanassov told journalists.
Police have said the 30-year-old journalist was brutally beaten, raped, and strangled, and that their inquiry was looking into both her personal and professional life.
The Bulgarian government has indicated Marinova's attack was not about her work.
But they said it does not appear that the murder was linked to her work as a journalist.
"It is about rape and murder", he said.
Sotir Tsatsarov confirmed the arrest of Severin Krasimirov, a Bulgarian citizen, but gave no further details. "Again a courageous journalist falls in the fight for truth and against corruption", the EU Commission's vice president Frans Timmermans tweeted late Sunday.
In 2017, UNESCO recorded a total of seven journalists killed in Europe, four of whom were women, representing the highest number of female reporters killed in single year, since 2006.
Authorities said she died from blows to the head and suffocation.
She was the director of TVN, a TV station in Ruse, and an anchor of two investigative programs.
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It. has politicians in the palm of its hand, " Costello, a spokesman for the Alliance for Gambling Reform, told the ABC. On Friday's 2GB Breakfast show Jones repeatedly yelled "we" own the Opera House over the top of his interview subject.
She interviewed the reporters behind the probe, investigative journalists Dimitar Stoyanov from the Bivol.bg website and Attila Biro from the Romanian Rise Project.
Through a United Nations spokesperson, Secretary-General António Guterres called on "all governments to strengthen press freedom and ensure there is accountability for crimes committed against journalists".
The Committee to Protect Journalists called on Bulgarian authorities to launch a thorough investigation.
He said: "Viktoria's death, the brutal manner in which she was killed, is an execution".
In what would be her final show to air, Marinova addressed the constraints of practicing journalism in her country.
The Bulgarian government has been under global pressure to investigate the murder.
At the Ruse vigil, telecoms technician Venelin Rumenov, 27, told AFP: "I don't think that she had been threatened or anything".