The Finn, re-signed by Ferrari for 2018, scorched to a record fastest lap in 1min 43.916sec around the spectacular Spa-Francorchamps cicuit on an overcast day in the forests of the Belgian Ardennes.

This was enough for him finish 0.197sec clear of championship leading German teammate Vettel with Briton Lewis Hamilton, who is 14 points behind in him in the title race, third for Mercedes.

Dutch driver Max Verstappen, backed by grandstands packed with his 'orange army', was fourth for Red Bull ahead of Finn Valtteri Bottas in the second Williams and Australian Daniel Ricciardo, in the second Red Bull.

Briton Jolyon Palmer, of Renault, was seventh ahead of Mexican Sergio Perez of Force India, Spaniard Carlos Sainz of Toro Rosso and two-time champion Spaniard Fernando Alonso in a McLaren Honda.

This was a remarkable effort given the team's power problems, while his team-mate, home hope Stoffel Vandoorne, was 14th. The Belgian faces a 65-place grid penalty after another overnight engine change penalty was added to his total.

After earlier rain, the track was wet at the start of the session, causing most drivers to venture out on intermediate tyres for the opening 10 minutes.

Once they switched to slick tyres, Hamilton was soon on top of the time-sheets before Raikkonen took over after half an hour. Both men were running on super-soft compounds.

Russian Daniil Kvyat lost power and parked his Toro Rosso at the side of Kemmel Straight where a minor fire was extinguished.

As the track dried, Ricciardo and then Verstappen put the Red Bulls on top, after switching to ultra-soft tyres before Raikkonen blitzed the track record in 1:43.916 to go top by 1.118sec.

Hamilton, also on ultras, then took second just 0.198 off the Finn's fastest lap before being outpaced and replaced by Vettel, by just 0.001sec.