(CNN)Bulgarian authorities are investigating the rape and murder of an investigative reporter in the northern city of Ruse, the third journalist to have been killed in the EU in the past year.
The body of 30-year-old Viktoria Marinova, who worked for broadcaster TVN, was found on Saturday near a pedestrian alley in an area with heavy vegetation, Bulgarian state media reported.
Preliminary investigations showed the cause of death was blows to the head and suffocation.
Bulgarian Interior Minister Mladen Marinov described the murder as "exceptionally brutal" and said Marinova was raped before she was killed, according to state media. He said the country's top murder investigators had been sent to Ruse to work on the case.
Investigators are working with a psychology team to produce a profile of the perpetrator but authorities have not yet identified a suspect.
It is not clear if Marinova's murder was related to her journalistic work. Authorities are working to identify witnesses and potential motives.
Bulgarian Interior Minister Mladen Marinov said investigators were looking into Marinova's professional and personal life. One theory they're pursuing is that the assault was an unplanned event, carried out by someone from a psychiatric facility in the vicinity of the crime scene.
"However, we do not exclude a version for planned action also by such a person or a personal motive. So, absolutely no version is underestimated," he said, according to state media.
Ruse Regional Prosecutor Georgi Georgiev told state media that Marinova's mobile phone, car keys, glasses and part of her clothing were missing when her body was found. As of late Monday, her mobile phone had not been found yet, said Commissioner Teodor Atanasov, head of the regional Interior Ministry directorate.
A friend of Marinova, Todor Gechev, told reporters from Bulgarian National Television (BNT) that he met with her on Wednesday. She told him she was working on a journalistic investigation but didn't feel worried about her safety and had not received threats.
Vigils in Marinova's memory were held Monday evening in Ruse, the capital Sofia and other cities.
Most recently Marinova anchored the program "Detector" on TVN, where she interviewed two journalists who were investigating alleged corruption involving European Union funds. Previously she hosted a lifestyle program and was involved with charity work. She was the mother of a young daughter.
"With enormous pain and insurmountable grief the team of TVN television is experiencing the loss of our beloved colleague, Victoria Marinova," TVN said in a statement. "Therefore we ask for sympathy for the sorrow of relatives and colleagues. A bow in her memory!"
The Committee to Protect Journalists called on Bulgarian authorities to conduct a "rigorous, thorough investigation" into the killing.
"CPJ is shocked by the barbaric murder of journalist Victoria Marinova," said CPJ European Union Representative Tom Gibson in Brussels. "Bulgarian authorities must employ all efforts and resources to carry out an exhaustive inquiry and bring to justice those responsible."
The organization added in its statement that Marinova's last broadcast was an interview with Romanian journalist Attila Biro and a Bulgarian colleague, Dimitar Stoyanov, who were looking into allegations of fraud involving EU funds, and that the two reporters were detained by Bulgarian police in September.
European Commission First Vice-President Frans Timmerman said he was "shocked by the horrendous murder." "Those responsible should be brought to justice immediately by the Bulgarian authorities," he said in a tweet.
