Nico Rosberg, Lewis Hamilton top Sochi practice times

Rosberg topped the timesheets in Sochi with a best lap of one minute 42.311 seconds, 0.065secs ahead of team-mate Hamilton - with the pair well clear of their next challengers.

Heading into the fourth-last race of the F1 season, the team-mates are poised to fight out the championship race - with Hamilton 10 points ahead of Rosberg.

Third-quickest on Friday was McLaren's Jenson Button (1:42.507secs), ahead of Ferrari's Fernando Alonso (1:42.720secs).

Kevin Magnussen (1:43.026secs) finished fifth in the other McLaren and Force India's Sergio Perez (1:43.129secs) rounded off the top six.

The only threat to the Mercedes pair in the drivers' standings, Daniel Ricciardo, struggled for early pace in Russia - setting a best lap of 1:43.821secs to leave him 12th quickest in the 90-minute session.

However, the Red Bull driver - who is 73 points behind championship leader Hamilton - was still better placed than his team-mate Sebastian Vettel.

The four-time defending F1 champion's season has never hit the heights of the four that preceded it, with Vettel's best lap of 1:44.506secs no less than 2.195secs slower than Rosberg's best as his struggles continued.

Only 21 drivers took part in the session, with Marussia having opted to run a solitary car in Sochi as a mark of respect for Jules Bianchi.

French driver Bianchi remains in a critical but stable condition in hospital after suffering a severe head injury as a result of a crash during last Sunday's Japanese Grand Prix at Suzuka.