Lewis Hamilton has admitted that he is concerned by the reliability that have affected Mercedes in recent races.

The Briton is on the verge of securing a third world title after winning the Russian Grand Prix in Sochi, but his teammate Nico Rosberg was forced to retire with a throttle problem early in the race.

Hamilton, who struggled for pace in the dying stages of the race, has suggested that the team need to work hard at making their cars more reliable ahead of the final rounds of the 2015 championship.

"I don't know what was wrong with my car, I don't think it was DRS, but it was something happening to the rear end, that's why my pace decreased," he told reporters.

"The reliability is something we have focused on a huge amount over the last year and a half and for whatever reason, we are struggling and having a few problems with it.

"Nico has been incredibly unfortunate to suffer the worst. We will be working as hard as we can to rectify it - and hope in the next races we don't have a problem - but of course it is a concern for us."

Sebastian Vettel finished second and Force India's Sergio Perez came home third.