Kimi Raikkonen impressed by Ferrari's progress

Sochi: Formula 1 driver Kimi Raikkonen said Ferrari have "surprised" themselves with their performance in some races this season, but admitted that the remaining weakness of their car won't be solved this year.

With five races left in the season, starting with the Russian Grand Prix here this weekend, Ferrari are second in the constructors' championship, two places and 159 points better off than they were at this stage of their winless 2014 season, according to Sky Sports.

Raikkonen acknowledged that Ferrari still don't have a car for all circuits, although he does believe they have continued to make good progress since the start of the campaign - as shown at Suzuka, a track which didn't automatically suit their car but where Raikkonen and Sebastian Vettel were only beaten by Mercedes.

"Certain tracks are trickier for our car depending on the layout right now. We know when it's going to be a bit trickier, but we have surprised ourselves," the 2007 World Champion said.

"We expected Monza to be a bit more difficult, we were quite good there. Suzuka wasn't too bad even though it shouldn't be our favourite place right now. But it shows that we are doing the right things and improving things."

Ferrari have won three races in 2015 -- all by Sebastian Vettel -- in Malaysia, Hungary and Singapore. Raikkonen's best came in Bahrain when he finished second.