MOSCOW—A star Russian ballet dancer and two others held in connection with an acid attack that nearly blinded the director of the Bolshoi Ballet have all signed written confessions, Moscow police said Wednesday.

Police said they believed leading solo dancer Pavel Dmitrichenko masterminded the Jan. 17 attack in which a masked assailant splashed sulfuric acid in the face of 42-year-old Sergei Filin, leaving him with severe burns to his face and eyes that required numerous surgeries to save his vision.

Moscow police said in a statement released Wednesday that the motive appeared to be related to a personal grudge stemming from behind-the-scenes intrigue at the famed dance troupe.

The brutality of the assault had stunned Moscow, where ballet stars are often revered as much as sports figures are in other parts of the world.

A spokeswoman for the Bolshoi declined to comment on Wednesday.