Following the attack, two more journalists were reportedly beaten on Monday: one a reporter with the Zhukovskiye Vesti suburban Moscow weekly, and another the editor of the Volga region's Saratovsky Reporter.
Criticising the Kremlin’s record on press freedom, US State Department spokesman Philip Crowley said journalists around the world must feel free to do their jobs “without fear of intimidation or physical violence".
"As the 2009 humanitarian rights report noted, eight journalists, many of whom reported, you know, critically on the government, were killed over the last year in Russia.
"With one exception, the government has failed to identify, arrest or prosecute any suspects."
Meanwhile European security group OSCE showed a "worrying trend" of violence against media representatives in Russia.
A grainy 90-second webclip, which swept through the internet, showed two assailants converge on Oleg Kashin and beat him with what appeared to be a lead pipe.
The attack has generated an unprecedented wave of solidarity between the state and opposition media.
President Dmitry Medvedev took the unusual step of responding to the assault immediately and promised to find and punish those behind it.
Thirty-two Russian journalists have been murdered since 1993 and more than 30 attacked this year.