He says shooting for SPL2 was grueling. "It was really horrific. In a scene in which the character I play is abused and tortured, I felt I almost died."

In a combat scene, Wu says, he was kicked almost 300 times and had to resort to ice bags to ease the pain every time the director halted the shooting.

Another star in SPL2 is Thai Tony Jaa, who recently drew international attention with his Hollywood debut in Fast and Furious 7.

Jaa, 39, began training in muay thai at a local temple when he was 8 and gained a black belt in taekwondo. He has won several gold medals in Thailand in athletics, fencing and gymnastics.

SPL2 is his first Chinese-language movie, he said in a recent video message to the media.

Jaa said that he felt "lucky to work with top Chinese action stars and has learned some Chinese kung fu from the brothers".

Zhang Jin, who started learning martial arts when he was 9, is another highlight of the movie.