SHANGHAI (Reuters) - The Chinese debut of Quentin Tarantino's Oscar-winning film "Django Unchained", a violent Western slave revenge tale, was suddenly cancelled on Thursday for "technical reasons," movie theatres said.

China is now the largest international market for Hollywood and the opening of the film had been widely anticipated because of reports it would only have minor cuts from government censors, despite Tarantino's reputation for violence.

Some microbloggers said the film had begun to roll when it was stopped and they were told to leave cinemas.

"We got the notice from our headquarters around 10:00 a.m. this morning but it was too late to cancel two viewings," said an official at one of several Shanghai theatres contacted.

"We were only told that it was due to some technology problems and were told to cancel it. They didn't tell us when the film would be shown again."

Domestic media quoted industry insiders as saying the cancellation was probably due to some nudity which may not have been edited out of the film.

The Chinese government censors all movies before they can be released. Scenes that contain nudity, politically sensitive issues, as well as extreme levels of violence, must be edited out before the film receives a go-ahead from the authorities.

Officials at Huaxia Film Distribution Co Ltd and the State Administration of Radio, Film, and Television (SARFT), which is responsible for movie censorship, could not be reached for comment.

"After watching it for about a minute, it stopped!" said microblogger Xue Yi Dao. "Staff then came in and said SARFT... had called to say it had to be delayed!! Can someone tell me what's happening!!"

The film stars Jamie Foxx as a slave turned bounty hunter who wreaks revenge on slave plantation owners as he tries to rescue his wife. It features Tarantino's trademark style of extensive graphic and bloody violence, along with dark humor.

Microbloggers speculated that a scene in which Foxx is strung from the rafters covered only by a thin cloth may have caught the attention of the authorities.

In 2004, the debut of a Chinese movie, "Dahongmidian", was also suddenly cancelled on the day it was supposed to open because it contained "erotic" scenes which "made improper propaganda without approval," according to local media reports.

Filmmakers are eagerly turning their eye to the vast Chinese market, where several new screens are being built every day, particularly after China eased its quota rules on U.S. movies last year.

It did not lift its annual quota of 20 foreign films, but essentially expanded it, permitting 14 premium format films such as IMAX or 3D on top of the original 20.

The Chinese box office for U.S. films grew by 36 percent in 2012, making the country the largest international market and surpassing Japan, according to the Motion Picture Association of America's MPAA's annual Theatrical Market Statistics report in late March.