The accident occurred while filming at the Ognyanovo reservoir in Bulgaria at about 7 p.m., when an explosion went awry. The injured stuntman is now reportedly in stable condition.
"It is with great regret that we confirm this unfortunate accident," a representative for the film's studio, Nu Image/Millennium Films, said in a statement provided to MTV. "Our hearts go out to the families and those on the production affected by this tragedy. The filmmakers are working closely with the authorities in responding to and investigating this accident."
The identities of the killed and injured stuntmen have not yet been released. The studio would not confirm the accident to TheWrap.
The film's stars, which include Sylvester Stallone (who's also producing), Jean-Claude Van Damme, Arnold Schwarzenegger, Bruce Willis and Chuck Norris, were not present during the accident.
This is the most recent tragic accident to occur on an overseas film set; in December, Australian stuntman Scott McLean was placed in a medically induced coma after a car crash on the set of "The Hangover Part II" near Bangkok, Thailand.
During the stunt, an oncoming car slid into a truck. Rainy weather that left the roads slick was believed to have played a part in the accident.