* Bolshoi artists publish open letter to Putin
* Some dancers say confession by top dancer "unconvincing"
By Thomas Grove and Maria Tsvetkova
MOSCOW, March 12 (Reuters) - Artists at Russia's Bolshoi ballet asked Vladimir Putin on Tuesday to order a new inquiry into the acid attack on the troupe's artistic director, fearing the dancer arrested for the assault was only a pawn in the case.
Three hundred performers said in a letter to Putin they believed Bolshoi star Pavel Dmitrichenko had only confessed to plotting the Jan. 17 attack that almost blinded Sergei Filin because of police pressure.
The Moscow police declined to comment, but the letter suggested there could be many more twists in a case that has shocked Russia and shone a spotlight on bitter rivalries at one of its most respected institutions.
The Bolshoi's management and Filin himself have suggested Dmitrichenko acted on someone else's orders to organise the attack, in which a masked assailant flung a jar of acid in the director's face outside his Moscow apartment.
"The conclusions of the investigation appear to us hasty and the proof unconvincing, and the confessions of Pavel himself a result of harsh pressure he was put under," said the letter addressed to Putin and others in the government and theatre.
"We are asking for an honest and unbiased investigation into the tragedy that happened to Sergei Filin," it added, requesting the creation of a commission to look into the crime.
Dmitrichenko, 29, who played the murderous Russian monarch Ivan the Terrible and the villain in Swan Lake, appeared in footage shown on state television last week looking haggard and tired as he confessed to organising the incident.
He has defended himself by saying he had not wanted acid used. His lawyer was quoted by the Rapsi legal news agency on Tuesday as saying that he was ready to agree to a plea bargain but would not accept full responsibility for the crime.
Two other men suspected of being Dmitrichenko's accomplices in the attack, including the man who allegedly threw the acid, also confessed to the crime. Moscow police say Dmitrichenko paid them 50,000 roubles ($1,600).
Interviewed on state television on Tuesday, Filin, wearing sunglasses and wrapped in heavy clothing that only exposed his nose and mouth.
"Someone pushed (Dmitrichenko) into it," said Filin, 42, from Germany where he is receiving treatment.
"Every moment, every meeting with Dmitrichenko for me was another threat, another demonstration of hostility and I don't want to hide that now."
SYMBOL OF CULTURE
The day after Dmitrichenko's confession, dancer Yevgeny Sazonov said, investigators assembled 200 of the theatre's performers to outline their version of what had happened in the case, which many dancers still refuse to believe.
Sazonov, a dancer with sandy blond hair, said more than half the dancers did not believe in Dmitrichenko's guilt.
"The whole story is unbelievable. It's unbelievable that this happened to Sergei, and it's unbelievable that Pavel took part in it," he said, speculating that police may have pressured Dmitrichenko into confessing.
The theatre, in the shadow of the Kremlin, is scheduled to perform Sleeping Beauty this month. Dmitrichenko had been cast as the Blue Bird but has been replaced.
A symbol of Russian culture since the time of Catherine the Great, the Bolshoi Theatre, which opened last year after a multi-million dollar renovation, has seen its share of scandal.
The ballet troupe has had five artistic directors since 1995, and a candidate for the post quit in 2011 after pornographic images of him were posted on the Internet.
Anatoly Iksanov, the longtime Bolshoi general manager, has depicted the acid attack as an effort to further blacken the reputation of the theatre's leadership and said he doubts that Dmitrichenko alone was behind it.
"There are an entire series of facts that suggest that someone else may have ordered the attack, maybe someone from outside of the theatre, and investigators should look into that," he said after the publication of the letter.
Media have reported Dmitrichenko's motive was his relationship with partner Anzhelina Vorontsova, a ballerina whom other dancers said Filin had "squeezed" out of the best parts.
In court, Dmitrichenko alleged "corruption" at the Bolshoi and accused Filin of favouritism in distributing grants. (Reporting by Thomas Grove; editing by Andrew Roche)