RUSE, Bulgaria — Bulgarian police have detained a Romanian citizen of Ukrainian origin for 24 hours and were checking his alibi as they investigated the rape and murder of TV anchor Viktoria Marinova, whose body was found in a park in her Danube hometown of Ruse.

"We have in custody a person whose alibi we are checking, but for the time being we do not have a concrete suspect. Work with him is continuing," the head of Danube regional police in Ruse, Teodor Atanasov, told reporters.

A government source familiar with the investigation had told Reuters earlier that a suspect had been detained.

Prosecutors are expected to hold a news conference later in the day as international pressure mounts on authorities.

Bulgarian television journalist Viktoria Marinova. AFP - Getty Images file

On her last aired TV show, on Sept. 30, Marinova introduced two journalists who were investigating alleged corruption involving EU funds. She said her regional current affairs show, "Detector," would carry out similar investigations.

Although no link has been established to Marinova's work, her death has angered many in the Balkans country where people are frustrated with rampant corruption and an inefficient judiciary, for which Bulgaria has been criticized by the European Commission.

Prosecutors have said the 30-year-old journalist, who was a presenter and anchor at a local television station, had been raped, beaten and suffocated. Her body was found on Saturday.

The U.S. embassy in Sofia tweeted that it was shocked by the journalist's "horrific murder".

"U.S. is ready to help authorities if needed to bring the perpetrators to justice," it said.

The European Commission has urged Bulgaria to conduct a rapid investigation into the murder.

Some local investigative journalists called on authorities not to play down the option that her murder might have been linked to her work as a journalist.

"I see deliberate attempts to marginalize this killing and manipulate the public opinion that Viktoria was a victim of a random attack or sexual manslaughter," said Assen Yordanov, founder of Bivol.bg, whose reporters were on Marinova's last show. He did not elaborate.

He said Marinova was the only journalist who had agreed to host his website's journalists to discuss their investigation into alleged high-level graft and misuse of EU funds.

Local people observed a vigil overnight and lit candles in front of her image. Many were stopping on Tuesday to put flowers to commemorate Marinova, who left a seven-year-old daughter.

"This is extremely frustrating. We do not feel safe at all or calm when such things happen. I did not know her personally, but as a mother I can only feel for her," said 28-year-old Denitsa Peicheva.