Doctors are battling to save the eyesight of Bolshoi Theater Ballet Artistic Director Sergei Filin, who was severely injured after a late-night attack in which a masked man threw acid in his face.
He was attacked late on January 17 as he was returning to his Moscow apartment.
Bolshoi Theater General Director Anatoly Iksanov said on January 18 that doctors were operating "in order to stop the [vision loss] process" and that he would later be sent to a specialized clinic abroad.
"The condition of Sergei Filin's eyes is seriously worrying, especially one of the eyes," Iksanov said. He added: "We have already agreed with a military burns clinic in Belgium that after [the eye surgery in Russia] they will accept him. We have also arranged an airplane, so right after the operation he will be transported to the burns clinic in Belgium."
The Moscow Health Department's chief, Georgy Golukhov, later said Filin had undergone a successful eye operation but did not confirm plans to have him sent abroad for further treatment.
Police investigate the scene in Moscow where Filin was attacked by an unknown masked assailant late on January 17.
Iksanov and other colleagues say they believe the attack is linked to Filin's work with the Bolshoi.
"There is no doubt that [the attack] is related to his professional activity," Iksanov said.
Bolshoi Theater spokeswoman Katerina Novikova said Filin had received threats in the past.
"Several days ago there was a post published on Facebook that was directed against Sergei Filin and aimed at causing a quarrel among Bolshoi Theater management," Novikova said. "Sergei Filin's personal e-mail account was hacked and it was used to discredit him in the eyes of Bolshoi Theater management. Sergei had warned about it before and said there was a group of people who were constantly threatening him."
Then a Bolshoi soloist, Sergei Filin, dances in Malta at a performance of Tchaikovsky's "Swan Lake" in 2007.
Russian media reports and some performers have spoken of tensions at Bolshoi over the repertoire and artistic direction of the renowned ballet company.
Filin, a 42-year-old former Bolshoi star dancer, was appointed artistic director at Bolshoi in 2011.
He is the sixth artistic director at the Bolshoi since 1995.
Based on reporting by Interfax and AP