Mikhail Beketov, editor-in-chief of the Khimki Pravda newspaper, was found unconscious after being badly beaten on Thursday near his home in the northwestern suburbs of Moscow.
"Police have launched a criminal investigation into the assault on Mikhail Beketov," the source said.
Beketov was rushed to a local hospital on Thursday in a serious condition suffering from head injuries, a broken leg and multiple contusions.
"Surgeons at the hospital operated [on Beketov] overnight and his condition is now stable, though serious," the source said.
The police official said it was too early to say whether the assault was related to Beketov's professional activities as a journalist.
However, Beketov had reportedly received numerous threats over his investigations. His car was torched in May allegedly as a warning to stop his independent probe into illegal attempts to clear large sections of the Khimki forest for construction.
Russia remains one of the world's most dangerous countries for reporters. According to data from the international organization Reporters Without Borders, 21 journalists were murdered in Russia between 2000 and 2007 and many reporters were subjects of physical attacks and threats.
