Six Greenpeace activists unfurled a banner that read "Arctic Oil? Shell No!" just before the race began, paragliding onto the roof in full view of thousands of spectators.
Two more activists managed to get onto the winners' podium during the award ceremony and a woman held out a message that read "Congratulations, now help us to save the Arctic".
"We are a bit confused down here because the crowd is booing and cheering and booing and we don't understand why," said the winner, Sebastian Vettel of Germany, with a big smile.
Greenpeace opposes drilling projects in the Arctic by Shell, a partner of racing stable Ferrari, and title sponsor of the Belgian Grand Prix.
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As part of a new campaign called "Save the Arctic", a Greenpeace icebreaker, the Arctic Sunrise, headed to the North Pole yesterday, defying a ban by Russian authorities.
Greenpeace said in a statement that 35 of its members had infiltrated Sunday's race, with the two activists who accessed the VIP area paying USD 4,550 each for the privilege.
"If Shell continues to want to drill in the Arctic, we will all lose. An oil spill in the Arctic would be a disaster threatening an area of breathtaking beauty," she said in a Greenpeace statement.