Bulgarian authorities are under mounting pressure at home and in Brussels to bring to justice those responsible for the brutal killing of the journalist Viktoria Marinova, who was reporting on alleged corruption.
The police have said they are looking into all possible motives but the founder of Bivol.bg, whose reporters were on Marinova's last show, said he feared authorities were downplaying the likelihood of links to her work.
Several months ago, she became the host of an investigative program called Detector.
He tweeted: 'Again a courageous journalist falls in the fight for truth and against corruption.
Marinova's killing - as a random act of violence or as a targeted hit - comes after two other cases that provoked concerns about press freedom in Europe.
Marinova is at least the third journalist killed in an European Union country this year, after investigative journalists Jan Kuciak of Slovakia and Daphne Caruana Galizia of Malta also turned up dead.
Harlem Desir, media freedom representative for the Organization for Security and Cooperation in Europe (OSCE) condemned the killing on Twitter, saying that he would closely follow the investigation. But a Bulgarian investigative online site owner called for an independent worldwide inquiry.More news: Ruby Rose Suits Up As Batwoman In First Look At Arrowverse Crossover
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"We need to find out quickly whether the murder is connected with Marinova's research into the misuse of EU funds", said Sven Giegold, a German member of the European Parliament.
He went on to state that the investigation was about "about rape and murder".
Amidst the events, vigils have been planned in Ruse, Vidin, Pleven, and the capital city of Sofia.
The motivation behind her killing remains unknown, and Bulgarian authorities say they have yet to establish a link between her death in the northeastern city of Ruse and her work as a journalist.
Bulgaria's Prime Minister, Boyko Borissov, told reporters a "large amount" of DNA had been collected.
"This is a topic on which no other Bulgarian national media dared to report on", he told The Associated Press on Monday. In August 2017, Swedish freelance journalist Kim Wall was reported missing and found murdered in October when she was researching a story on Danish inventor Peter Madsen. Slovak journalist Jan Kuciak was shot dead along with his fiancee in an attack linked to his reporting on tax evasion in February this year.
The press office of the European anti-fraud unit OLAF said it was "aware of allegations concerning possible misuse of EU funds in Bulgaria that have been brought to light by journalists in recent weeks".
The pair were briefly detained by police while attempting to stop the destruction of documents linked to the scheme, drawing condemnation from Reporters Without Borders (RSF).