One of the kung fu instructors kicked Leung during a practice session on Monday, breaking a bone in his left forearm, Agnes Leung, a publicist at Wong's production house Jettone Films, told The Associated Press in a phone interview.
Leung must rest his arm for several weeks but can continue to train on his kicks, she said.
Wong's movie about Ip Man, who trained Lee for five years when he was a teenager, was tentatively scheduled to start shooting in September but might be delayed depending on Leung's recovery, she said.
Wong's biopic will be the second about Ip in recent years. Hong Kong action star Donnie Yen played Ip in a 2008 Wilson Yip film named for the pioneering martial arts master.
Wong's version is being closely watched because it marks a rare departure by the Cannes-winning director from the art-house fare for which he is best known.
The director's most recent film and his English-language debut, "My Blueberry Nights," starred singer Norah Jones, Jude Law, Rachel Weisz, Natalie Portman and David Strathairn.
Leung is known for playing subdued characters like the melancholy writer who had a love affair with a married woman in Wong's "In the Mood for Love." That performance won him best actor honors at the Cannes Film Festival in 2000. He most recently starred in John Woo's two-part Chinese historical epic "Red Cliff."
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