Lewis Hamilton won a dramatic Belgian Grand Prix at Spa to maintain his lead at the top of the Formula One World Championship.

Hamilton all but secured victory in the penultimate lap where reigning world champion Kimi Raikkonen of Finland spun off the course as the pair battled the slippery road conditions prompted by a late spell of rain.

It was an experience and a half," Hamilton said. "I was praying for rain. I wanted it to come because I knew how to deal with it. The heavens opened and I saw Kimi begin to back off and to brake a bit earlier.

"I was going reasonably wide at Turn 12 but Rosberg spun and went off where I was coming back on. I went over the grass. It was incredibly tough.

"Kimi pushed me wide. I was a little bit ahead. I was outside on Turn One, I had no room and he basically pushed me so I went on the escape route.

"So I let him past, then got in his tow and he was ducking and diving left and right but I managed to get past him and I was pretty much gone from there."

A chaotic final lap saw BMW Sauber's Heidfeld jump from eighth to third place after the team decided to change to wet-weather tyres at the start of the final lap. Renault's Fernando Alonso followed suit to secure fourth place.

The 23-year-old Englishman is now eight points ahead of Brazilian Felipe Massa of Ferrari in the championship after luckless defending champion Kimi Raikkonen of Finland crashed out in the final laps after dominating.

The race was settled by the capricious weather conditions as Massa came home second and German Nick Heidfeld stole through to take third for BMW Sauber.

Raikkonen had taken the lead at the start of the second lap when Hamilton spun at the La Source hairpin, but after controlling the race he lost his lead and his title challenge when he crashed out in heavy rain in the closing laps.

It was Hamilton's fifth win this year and his ninth in Formula One in two seasons.

"It was an experience and a half," said Hamilton. "I could see Kimi ahead and after the second stop he was so far ahead, I didn't know he had made a gap. I was pushing, pushing, pushing, I was catching him one-tenth a lap.