UPDATED SUNDAY: Moscow police have revealed that Bolshoi Ballet director Sergei Filin was attacked with sulphuric acid, causing third-degree burns to his face and eyes. As he recovered today from a second round of surgery on his damaged eyes, his public rival described the assault as "monstrous". The star dancer Nikolai Tsiskaridze, who has been widely accused of inspiring fanatical opposition to the current Bolshoi management, today condemned the attack.

It was in contrast to yesterday when, challenged by a journalist to answer, Tsiskaridze had curiously evaded any comment on the incident, saying that it was nothing to do with him. He went on that Filin had described him as a "polecat" in leaked emails on a Facebook page that the Bolshoi Theatre says was faked by a hacker. Tsiskaridze said nasty things often happened and always would happen in the theatre, and he believed secret business deals or a love affair was behind the use of acid.

The extent of the hostility between factions inside the theatre was underlined when earlier in the day the Bolshoi general director Anatoly Iksanov stated that he was certain the attack on Filin was intended to get him out of his job. It has emerged that Tsiskaridze's supporters had written to President Putin late last year urging him to sack Filin and Iksanov, and replace them with the dancer, who is a popular television celebrity and is strongly linked with the old guard at the Bolshoi.

However, the overwhelming reaction from Bolshoi personnel as well as Russia's politicians has been shock and outrage. Moscow police are treating it as a crime of grievous bodily harm.

Yesterday (Saturday) Filin was reported to have had further surgery on his eyes, and doctors say it will be up to three weeks before they can assess how his vision is affected.

The incident happened late Thursday night, when a masked man attacked him with what's now said by police to be sulphuric acid outside his Moscow home. The former star dancer, 42, who has been Bolshoi ballet director for almost two years, received severe acid burns over his face, head and neck.

From his Moscow hospital room, with his head fully bandaged, Filin told Russian TV reporters (picture right from TV) he at first believed he was about to be shot when a masked man confronted him and shouted his name. When he turned, the attacker threw a jar of caustic liquid into his face.

He was said to accept the priority to save his eyes before he can undergo specialist treatment to the third-degree burns to his face and head. He is likely to need plastic surgery and the Bolshoi management said doctors advised treatment might take six months.

Yesterday chief physician at the 36th central Moscow Hospital, Alexander Matichkin, announced that first surgery on Filin's eyes had gone well without complications, and he had been moved out of intensive care into a regular ward. He is walking and eating, but is totally blindfolded and will face extensive further surgery. It will be 14-21 days before the state of his vision can be known, said the specialist. It's thought one eye may be relatively unscathed.

Filin's Facebook page had recently been hacked and emails apparently from him exposed, though it is said these were faked

The attack came after weeks of threats, including his tyres being slashed and menacing phone calls to his home. Filin's Facebook page had recently been hacked and emails apparently from him exposed, though it is claimed that these were faked.

According to his wife, the Bolshoi dancer Maria Prorvich, the threats had mounted in the past few days. She said: "I now fear for his life, even for those of our children."

Bolshoi general director Anatoly Iksanov told reporters: "The aim of this attack was to undermine the theatre management. Sergei told me yesterday that he knew he was on the front line."

There was instantly fervent interest in what Tsiskaridze would say. After his voluble counter-accusations yesterday, today Tsiskaridze said that what happened to Filin far exceeded the traditional Bolshoi hostilities of ground glass in pointe shoes and dead cats thrown onstage, but that "such things would never change".

He said: "To splash acid in the face is a terrible crime, which not only disfigures the person's life, but takes away his ability to operate, basic eyesight. This is monstrous."

To splash acid in the face is a terrible crime, which not only disfigures the person's life, but takes away his basic ability to operate, his eyesight

The Bolshoi prima ballerina Svetlana Zakharova expressed horror at the "animalistic cruelty" of the attack on her long-time dance partner.

The theatre's press spokeswoman Ekaterina Novikova said: "The incident is a colossal blow to the country’s image. The ballet world is in shock. It’s important that investigative bodies find who stands behind this monstrous attack as soon as possible. It was a targeted strike."

The Bolshoi Ballet is to return to London this summer, three years after its last visit, to perform a three-week season at the Royal Opera House. It is the first as director for Filin, who as a dancer was greatly admired by London critics.

According to Filin's mother Natalia Filina the threats started on the night of 31 December. The date may be significant, as it was just after Iksanov and Filin gave Tsiskaridze a public dressing-down in an interview with The Russian Gazette, in which they addressed an attempt by his supporters to get President Putin to sack them and install him as chief. On 31 December, which is also Tsiskaridze's 39th birthday, he was ordered to dance in The Nutcracker.

Tsiskaridze, who has described himself as the world's greatest dancer and inspires fanatical factions, has long declared his ambitions to take over the ballet troupe, but was passed over twice. Never shy of saying exactly what he thinks, he recently accused Filin of trying to limit his teaching and performances, and described the atmosphere within the Bolshoi as Darwinian - "if you don't eat them, they'll eat you," he said.

Notably in the Russian Gazette interview Filin put Tsiskaridze humiliatingly in his place, declaring that the dancer would perform in The Nutcracker on 31 December, because it was the director who made the decisions. Iksanov also described the dancer as a "trouble-maker" who was "pouring dirt" on his mother theatre.

Since the campaign of phone calls began that night, it is possible that a crazed fanatic took it into his own hands to take vengeance. Menacing pressure from adoring supporters against their idols' rivals is not unusual, and the Bolshoi ballet director's post has never been comfortable.

Boris Akimov, ballet director from 2000 to 2003, said yesterday that he himself had experienced highly unpleasant pressure on behalf of disgruntled performers.

"Judging from the scale of pressure put on Filin - the silent phone calls, evil emails, punctured tyres - you have to think this has been well organised and targeted on one person, to make him quit his post," said Akimov. "But by whom and for whom was it intended to clear him out of the way?"

The Bolshoi has many diseases: a loathsome claque,... half-crazy fanatics prepared to bite the throats of any rivals to their idols

His successor as ballet director, Alexei Ratmansky, 2004-8, endorsed the grimness of the job in a theatre where jungle politics rule.

Now resident choreographer at American Ballet Theatre in New York, he wrote on his Facebook page on Friday: "The attack on Sergei Filin is no accident. The Bolshoi has many diseases: a loathsome claque,... half-crazy fanatics prepared to bite the throats of any rivals to their idols,… placing lies and scandalous interviews in the press. This is one giant snowball, and its cause is the gradual collapse of theatrical ethics at the Bolshoi and among certain individuals. That is the real trouble with this great theatre."

Filin's immediate predecessor as Bolshoi ballet director, Gennady Yanin, was fired after being embroiled in an internet porn scandal, which some claimed was a set-up.

All these scandals have happened to ballet directors during term of the Bolshoi's current theatre director, Anatoly Iksanov, in post since 2000. He had the unenviable task of taking over in the turbulence that followed the post-Soviet era, during which the Bolshoi Theatre had become a tool for influence in political and business circles. The battle to introduce more open, Western-style artistic directorship, and dissipate the institutionalised tyranny of the long Soviet period, has not been easy, with large numbers of "old guard" insisting that modernisers are betraying true Russian values.

Iksanov insisted that Filin was a firm but fair director, holding both Russian traditions and the need for more modern European-style openness in balance. A former star dancer with the Bolshoi, Filin (pictured with Svetlana Zakharova, © Bolshoi Ballet) was appointed director less than two years ago amid fierce rivalries for the leadership of the famous ballet company, including - very explicitly - that of Tsiskaridze.

Infighting at the Bolshoi, always viciously partisan in the Soviet era, resurged after the dismissal in 1995 of the longtime Soviet-era ballet director Yuri Grigorovich, who ran the Bolshoi for 30 years through the Cold War and beyond. The next decade saw a rapid ebb and flow of directors, each attempting in vain to counter the entrenched old guard and bring the Bolshoi fresh ideas. Four years ago the veteran Grigorovich returned to effective control as resident choreographer, ensuring that his productions remained the centre of artistic policy.

Just turned 86, he retains almost god-like status for his supporters, who include many veteran Bolshoi coaches as well as some celebrated dance stars such as Tsiskaridze, who share a suspicion of modernisers. In a country where ballet has unimaginable clout and glamour in political and business circles, fanatical differences go well beyond polite artistic debate. They are characterised as ideological, nationalistic, even historic, pitting reactionaries against progressives, "true Russians" against "decadent" Westernisers, and skulduggery is all too common among some followers.

Grigorovich supporters were accused of hounding out the most significant recent director, the gifted choreographer Alexei Ratmansky, who was viewed outside Russia as guiding the hidebound Bolshoi out of its perception as a Soviet relic into a creative company of top rank during his five-year tenure. Tsiskaridze was a thorn in Ratmansky's flesh, and led a sizeable faction who despised the choreographer for never having danced in the Bolshoi.

The theatre must deal with the appalling animosities that have made the Bolshoi more famous for poisonous scandal than for dancing

Despite a cautious feeling that Filin's appointment in 2011 signalled a new beginning for the Bolshoi, anxiety that some dancers were trying to make the rules has steadily mounted inside the company, which with 200 dancers is supremely competitive for roles.

Filin's first year suffered a heavy blow when the Bolshoi's celebrated new stars Natalia Osipova and Ivan Vasiliev quit the company and moved to St Petersburg's privately-run Mikhailovsky Ballet. In the December interview with Russian Gazette Filin and Iksanov answered suggestions that the pair were motivated more by money than anything else, by saying that Osipova had spent most of the year guesting abroad already, with full agreement, and to quit after such special treatment had been granted her had infuriated them.

Despite this, Filin had swallowed his anger to invite the pair to reappear with the Bolshoi on their tour to the Royal Opera House this July and August, in order to please the London public who adore the couple. Iksanov admitted in the interview that this decision had caused much offence among Bolshoi dancers. In March Osipova and Vasiliev will also be the star attraction on the Mikhailovsky's London tour at the Coliseum.

The cost of Filin's treatment will be paid by the Bolshoi Theatre, said Iksanov. However, Izvestia reported that lawyers say if Filin significantly loses vision, he cannot count on the Bolshoi Theatre being liable to compensate him. Being the victim of a crime, any damages would be paid to him by the convicted attacker. Even were the attack to be firmly linked to office politics, the theatre would not be liable - as it would, for instance, had he tripped on a ladder left carelessly in the corridor.

The crime has created yet another destabilising vacuum at the head of the country's most important ballet troupe. While work continues - not least the London tour, which the Bolshoi always considers its key European date - it opens up the prospect of yet more internecine dispute over the top job. There will surely be clarion calls in the theatre to deal with the appalling animosities that in recent years have made the Bolshoi more famous for poisonous scandal than for dancing.

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