A man has been arrested over the rape and murder of Bulgarian television reporter Viktoria Marinova, who had highlighted possible government corruption, police said.

Teodor Atanassov, chief police officer of the northern town of Ruse, said officers are holding “a Romanian citizen of Ukrainian descent” for 24 hours, but he has not been formally declared a suspect.

Prosecutors said late on Monday that they had opened an investigation into the suspected misuse of European Union funds, as police investigate the rape and murder of Ms Marinova, whose strangled body was found on Saturday dumped near the Danube River.

Ms Marinova, 30, hosted a show last month featuring two investigative journalists who were detained for their work on suspected fraud involving EU funds.

A vigil for murdered television reporter Viktoria Marinova
A vigil for murdered television reporter Viktoria Marinova (Vadim Ghirda/AP)

The interior ministry said prosecutors were investigating GP Group, a large private Bulgarian building company alleged to have misused the EU money, and froze 14 million euros (£12 million) in assets.

While Ms Marinova did not appear to have been closely involved in the fraud investigation, her show touched on a sensitive subject in Bulgaria, where corruption is endemic.

The Balkan nation joined the EU in 2007 and was ranked 71st on Transparency International’s corruption list last year.

Joining the bloc opened up an enormous amount of possible new funding for Bulgarian infrastructure projects and other programmes designed to bring the nation up to EU standards.

Journalists’ groups and European leaders expressed shock at the murder.

Margaritis Schinas, spokesman for European Commission President Jean-Claude Juncker, said the commission expected “a swift and thorough investigation … that will bring those responsible to justice and clarify whether this attack was linked to her work”.

He quoted Mr Juncker as saying previously that “too many” journalists are being intimidated, attacked or murdered and “there is no democracy without a free press”.

A child lights candles next to a portrait of Viktoria Marinova
A child lights candles next to a portrait of Viktoria Marinova (Vadim Ghirda/AP)

The German government sharply condemned the killing, with the Foreign Ministry saying it was imperative “that there’s a fast investigation and that this horrible event will be illuminated as comprehensively as possible”.

Bulgarian interior minister Mladen Marinov insisted on Monday there was no evidence to suggest the killing was linked to Ms Marinova’s work.

She was a director of TVN, a TV station in Ruse, and a TV presenter for two investigative programmes.

Her final show on September 30 was about Attila Biro, an investigative journalist with the Rise Project Romania, and Dimitar Stoyanov from the Bulgarian investigative site Bivol.bg.

The two men were briefly detained on September 13 south of Sofia as they investigated a tip that documents connected to suspected fraud involving EU funds were being destroyed.

Bivol.bg owner Assen Yordanov said he could not directly link Ms Marinova’s murder to her work, but noted her show tackled “our very sensitive investigation into the misuse of EU funds”.

“This is a topic on which no other Bulgarian national media dared to report on.”

Mr Biro said he had never met Ms Marinova, but one of her colleagues had interviewed him and Mr Stoyanov about their work.

“They are on the right path, but let’s see how the investigation proceeds,” he said.