An international press freedom organization has sought to raise Bulgarian PM Boyko Borisov's awareness of instances of harassment of journalists working with an independent investigative website.

Addressed to Borisov, a letter by the Committee to Protect Journalists is voicing its concern over intimidation of reporters at Bivol, the biggest investigative reporting network of Bulgaria, and incidents related to a reporter who "in recent weeks... was followed and his home was broken into."

Bivol is the Bulgarian partner of WikiLeaks and also works with the Organized Crime and Corruption Reporting Project.

CPJ suggests the incidents are related to Bivol's claims of involvement of a Bulgarian bank, the First Investment Bank, in an EU funding scam investigated by the EU anti-fraud service, OLAF.

A FIBank official is quoted as telling CPJ the investigation is targeting "a corporate client" and not the bank itself.

The international press freedom organization is also warning of a harassment campaign against being led by several of media outlets in Bulgaria, namely "the daily newspapers Monitor and Telegraf, the weekly Politika, and Kanal 3 television", which are part of the media group of controversial MP Delyan Peevski and his mother, Irena Krasteva.

It also informs of an unannounced visit by Kanal 3 crew to the Paris apartment rented by Atanas Tchobanov, a Bivol reporter and editor, at a time he was traveling.

A copy of the letter, signed by CPJ Executive director Joel Simon, has also been sent to a number of Bulgarian and EU officials. These include Bulgarian President Rosen Plevneliev, Bulgaria's Ambassador to the US Elena Poptodorova, European Council President Donald Tusk, and the EU foreign policy chief Federica Mogherini.

"We ask that you use the authority of your office to ensure that the threats against Bivol are fully investigated and to guarantee the safety of its journalists," the letter also reads.