Investigative Bulgarian journalist, Hristo Hristov, whose work focuses on the secret files of the former Communist State Security, DS, has received an anonymous death threat.

Hristov informs on his own site desebg.com that he found the anonymous note in his mailbox at home. It has been written on the margin of a copy of his 2011 interview titled "The Indifference to Our Recent Past Is Detrimental."

Hristov has sent all evidence to the police with a copy to the caretaker Interior Minister.

The site desebg.com is the outlet where he publishes his findings.

The journalist writes he has decided to make the case public as threats against him have escalated in recent months and have now been directed towards his family as well.

"I find it unacceptable in the 21st century in an EU Member State to use DS methods to scare journalists. Such threats are a blatant violation of freedom of speech," he says.

Since the beginning of 2013, this is the third attempt to intimidate Hristov. His site became the target of a hacker attack right around New Year's Eve, while his family car has been intentionally damaged in March.

In the summer of 2006, the journalist received a threat he would be blasted with explosives if he did not stop his media publications.

In addition to the Communist State Security files, in 1999 – 2000 he worked on an investigation and a book dedicated to the DS murder of Bulgarian dissident writer Georgi Markov. During that period his home has been burglarized three times.