Downey Jr plays an industrialist who invents a high-tech suit of armour
Hollywood actor Robert Downey Jr has signed up for a sequel to comic book adaptation Iron Man, due to be released in 2010, Marvel Studios has said.
The first Iron Man film was released at the weekend and took $98.6m (£50m) in three days in the US and Canada.
Following its success, a string of new movies based on other comic characters will be made.
They will include Thor, Captain America and The Avengers - a group of heroes not connected to the British TV series.
Kevin Feige, head of production for Marvel Studios, said much of Iron Man's success was down to Downey Jr.
"It's great to see a sold-out audience that you know is made up of comic book fans and people who had never read an Iron Man comic in their life," he said.
Downey Jr plays a billionaire industrialist who invents a hi-tech suit of armour that transforms him into a superhero, with Gwyneth Paltrow playing his personal assistant.
Iron Man's takings represent a successful comeback for the actor, whose battles with drugs had seen his career suffer in recent years.
Early estimates said the film had taken $101m (£51m) in its opening weekend in the US and Canada, but final takings showed it had fallen just short of the $100m mark.