A television journalist has been brutally murdered in Bulgaria's northern town of Ruse, prosecutors said Sunday, in a case that has sparked international condemnation.

The body of 30-year-old Viktoria Marinova, whom authorities identified only by her initials, was found on Saturday in a park, Ruse regional prosecutor Georgy Georgiev said.

The death was caused by blows on the head and suffocation, he added.

"Her mobile phone, car keys, glasses and part of her clothes were missing," Georgiev said, adding that prosecutors were probing all leads - both personal and linked to Marinova's job.

Interior Minister Mladen Marinov later confirmed to journalists that the victim had also been raped.

Prime Minister Boyko Borisov expressed hope that the investigation would succeed because of the "work that has been done. Thanks to the large amount of DNA material collected it is just a matter of time before the perpetrator will be found."

Police sources told AFP that the crime did not immediately appear linked to her work.

The OSCE's media freedom representative Harlem Desir condemned Marinova's killing on Twitter: "Shocked by horrific murder of investigative journalist Victoria Marinova in #Bulgaria. Urgently call for a full and thorough investigation. Those responsible must be held to account."