A prominent Russian journalist who was also a huge critic of Russian president Vladimir Putin has died after getting severely beaten in what is being called a ‘mysterious death.’

Nikolai Andrushchenko, 73, was attacked by ‘unknown assailants’ in St. Petersburg last month. He spent the last six weeks of his life in a coma. Andrushchenko co-founded weekly newspaper Novy Peterburg and was known for publicly criticizing the government and Putin.

Andrushchenko’s death was reported by Russian media outlets that cited his lawyer and the editor-in-chief of the Novy Peterburg newspaper. State news agency RIA Novosti reported Andrushchenko, 73, had been in a medically induced coma since the March 9 attack, Fox reports.

Andrushchenko’s attackers have not been identified. The editor of RIA Novosti has linked the assault to articles in the newspaper about corruption in St. Petersburg.

Andrushchenko was a member of the St. Petersburg city council from 1990 until 1993. He was among the founders of Novy Peterburg, where he made a name for himself writing about human rights issues and crime.

He was jailed in 2007 for defamation — but his colleagues said the court was punishing him for its news coverage giving a voice to the opposition, according to the Committee to Protect Journalists.

Jacob Bojesson at The Daily Caller reports that Russian journalists are frequently targeted for their work. A 2009 investigation by the International Federation of Journalists reported 96 killings of journalists between 1991 and 2009 in Russia, by far the highest number among the 20 richest countries in the world.

Another rolling report from the Committee to Protect Journalists (CPJ) collects data of journalists killed in each nation from 1992 on. Only cases where the motive has a clear correlation to the victim’s work as a journalist make the lists.

There have been 56 such cases in Russia since CPJ started collecting data in 1992. Of the killings in the report, 58 percent are believed to have been carried out by either a military or government official. Just 11 percent have been solved.