Most worldwide media organisations underlined that the last aired report featuring Marinova was an interview on her new TV show, Detector, where her colleague interviewed Romanian investigative journalist Atila Biro from Rise project and his Bulgarian colleague Dimitar Stoyanov from Bivol, regarding alleged large-scale fraud linked to the misuse of European Union funds by the infrastructure company GP Group. Police said she had been brutally beaten, raped and strangled.
Her mobile phone, vehicle keys, glasses and some of her clothing were also found to be missing.
"We call for police protection to be provided for the TVN journalists who [also] worked with Viktoria Marinova on the same sensitive report, pending the outcome of the investigation", Reporters Without Borders, a French NGO, said.
Dimitar Stoyanov, of the Bivol website, and Attila Biro, from the Romanian Rise Project, have alleged a ring of consultancy firms... "Again a courageous journalist falls in the fight for truth and against corruption", the EU Commission's vice president Frans Timmermans tweeted late Sunday.
Ms Marinova is the third journalist to have been murdered in the European Union in a year.
Victoria Marinova, a 30-year-old Bulgarian journalist, was murdered in the town of Ruse, Buglaria on Saturday.
Bulgarian officials said there was no evidence to suggest that Marinova's killing was related to her work.
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European Commission spokesman Margaritis Schinas said the commission expected "a swift and thorough investigation" of Viktoria Marinova's death "that will bring those responsible to justice and clarify whether this attack was linked to her work".
Marinov said investigators are now working to identify any "contacts and problems" she had before the murder.
On September 10, Bivol - as a part of a series of journalistic investigations sponsored by the European Union - published a report on wide-scale and widespread corruption while allocating the European Union projects' funds.
Bulgarian Prime Minister Boyko Borissov: "I am convinced it is a matter of time before the murder would be revealed".
Bivol's owner Asen Yordanov stated that the murder of Marinova is a warning for other journalists. A German Foreign Ministry spokesman said that it's imperative "that there's a fast investigation and that this disgusting event will be illuminated as comprehensively as possible".
Marinova was a host of a Detector show on Bulgaria-based television channel TVN.
Bulgarian media reported Monday that the park where Marinova was killed is adjacent to a psychiatric facility and authorities were investigating whether a patient could have been Marinova's attacker.
The Committee to Protect Journalists said it was "shocked by the barbaric murder". He accused the mainstream media of leading a "massive smear campaign" against him.