Japanese police say an actor has died after getting stabbed in the stomach during a rehearsal with what is believed to be either a real or mock samurai sword.

Tokyo police said on Tuesday they were investigating whether the death was criminal or accidental.

Daigo Kashino, a 33-year-old theatre group actor, was rehearsing with several people at a Tokyo studio on Monday when the incident occurred. He was rushed to a hospital, but died hours later. Media reports indicated nobody was watching exactly how it happened.

Japanese public broadcaster NHK reported that other members of the theatre group rehearsing with Kashino said they saw him hunched over as they turned around after hearing him groan.