A leading Russian journalist for the Kommersant newspaper has been severely beaten outside his Moscow home.
Russian media said Oleg Kashin was in hospital in an induced coma and police were treating the attack as a case of attempted murder.
President Dmitry Medvedev has said "the criminals must be found and punished."
Mr Kashin's editor said the attack was retribution for articles he wrote. He has recently covered anti-Kremlin protests and extremist rallies.
Kommersant editor Mikhail Mikhailin told Moscow radio: "It's clear that the people who did this did not like what he says and writes."
The Russian prosecutor general will personally oversee the case, according to Tass news agency.
Kommersant said in a statement that Mr Kashin was attacked outside his Moscow apartment building in the early hours of Saturday. He had a fractured jaw, broken shins and injuries to his fingers and skull.
In recent months Mr Kashin had been reporting on demonstrations against the building of a highway through Khimki forest outside Moscow which has now been put on hold by the government.
Attacks on Journalists are not uncommon in Russia. Human rights groups say there have been 19 unsolved murders of journalists since 2000 and that investigations into attacks lead nowhere.
BBC Russian affairs analyst Damien McGuiness says Mr Kashin is a well-known figure and the newspaper he works for is one of Russia's most respected publications. He says solving this case will be seen as a test for just how serious the Kremlin really is about clamping down on the intimidation of journalists.