The Singapore film Apprentice has been passed uncut and given an M18 classification by the Media Development Authority (MDA).

This has come as a surprise to many in the film community, who expected that the drama about a young prison officer taken into the confidence of an executioner would get a milder PG13 or NC16 classification. An M18 rating means that only those aged 18 or older can view the film, thus reducing the size of its audience.

On the MDA's Films Classification Database website, the film is described as having "detailed depictions and descriptions of the execution process".

Films with depictions of the death penalty have been awarded a range of ratings in Singapore. The biopic Dead Man Walking (1995), for example, has a PG rating. The home video version of The Green Mile (1999) is rated M18, but the version released in cinemas at the time had a PG rating because it had been edited to fit PG requirements.

Apprentice, directed and written by Boo Junfeng, was honoured at this year's Cannes International Film Festival by being selected for the Un Certain Regard section.

In response to The Straits Times queries about Apprentice's rating, an MDA spokesman said: "Apprentice was rated M18 as it contains mature content including detailed descriptions of the execution process, as well as depiction of an execution. This is reflected in the consumer advice so that the public can make a more informed decision."

The film has been made with help from the MDA in the form of a production assistance grant, a development assistance grant (for script development) and a Film Mentorship Initiative, which helps pay for costs related to going overseas for training.

The story is told from the viewpoint of a young prison officer Aiman (Singapore actor Fir Rahman), who becomes friends with an older officer Rahman (Malaysian veteran Wan Hanafi Su). He turns out to be the prison's hangman. Aiman is drawn into a conflict that pits family loyalties against growing affection for his new friend.

Boo, 32, who is in Sydney this week for the Sydney Film Festival's screening of his work, sent a response by e-mail.

"I was hoping Apprentice would get at most PG13 in Singapore, considering it's rated PG for its release in France. I believe MDA gave it a lot of consideration and M18 was the best it could offer."

The producers told The Straits Times they do not plan to appeal the rating as they want to release the film without further delay.

Ms Tan Fong Cheng, one of the film's producers, says she is "puzzled" by the M18 rating. "Nevertheless, we respect the MDA's decision, but hope audiences will decide for themselves if the film warrants the rating."

Apprentice will be in cinemas from June 30.