The film which actor Heath Ledger was working on when he died is to be completed with actors Johnny Depp, Colin Farrell and Jude Law replacing him, the movie's director was cited on Tuesday as saying.

The Australian star was acting in 'The Imaginarium of Doctor Parnassus', directed by Terry Gilliam, before he died in January from a lethal mixture of prescription drugs.

There had been suggestions that the movie would be completed using digital technology, but Gilliam said in a statement that the three star actors had agreed to stand in for Ledger.

"I am grateful to Johnny, Colin and Jude for coming on board and to everyone else who has made it possible for us to finish the film," he said in the statement, cited by British newspapers.

"I am delighted that Heath's brilliant performance can be shared with the world. We are looking forward to finishing the movie and, through the film, with a modicum of humility, being able to touch people's hearts and souls as Heath was able to do."

Ledger, who gained international stardom with his Oscar-nominated performance as a gay cowboy in 'Brokeback Mountain', died in New York on 22 January. He was 28 years old.