Japanese police officers stand guard in front of a movie theatre showing The Cove in Yokohama, near Tokyo, on Saturday as protesters blast slogans and wave flags. ((Itsuo Inouye/Associated Press))

Protests greeted the Japanese cinema openings of The Cove, an Oscar-winning documentary about an annual dolphin kill at a Japanese village.

At Image Forum, an art theatre in Tokyo, about 30 noisy demonstrators waved Japanese flags and called out slogans against the film at its Saturday opening. Police had to get between protesters and the few supporters of the film outside the cinema after a shoving match erupted.

The documentary is being shown at only six cinemas starting this weekend. Another 16 theatres have signed on for screening at a later date.

Nationalist groups say the film is anti-Japanese and is connected with a militant anti-whaling organization, the Sea Shepherd Conservation Society. They're also upset over a contention in the film that much of the whale meat being sold in Japan is actually dolphin meat with high levels of mercury, a fact that has been challenged by government officials.

The film's producers have put in some disclaimers in their Japanese version saying the statistics in the documentary were gathered by and are the responsibility of the film's creators. As well, the faces of most Japanese in the film have been blurred out.

The Cove centres on Ric O'Barry, a former trainer for the Flipper TV show, who is leading an anti-dolphin kill campaign.

The film used hidden cameras to show scenes of the annual dolphin kill in the village of Taiji. It features local officials and fishermen defending it as a tradition with a long history.

Fishermen from the village say they are angry about being shown in the film without their permission.

Due to the aggressive demonstrations against the film's screening in Japanese cinemas, many theatre owners decided to cancel the screenings in early June.

That triggered a national debate about freedom of speech with prominent journalists, filmmakers and lawyers urging the cinemas to show the documentary.

The movie's Japanese distributor, Unplugged Inc., and Yokohama New Theatre, a small cinema near Tokyo, obtained court orders to keep protesters away.