Family groups renewed calls on Friday to clamp down on video game Manhunt 2 after hackers accessed scenes of bloody killings that were scaled back to let the game go on sale in the United States.

The feat involves modifying Sony Corp's PlayStation Portable device to run an altered version of Manhunt 2 and led to calls for a more restrictive rating on the game.

The Entertainment Software Ratings Board, the U.S. industry group that polices game content, on Friday defended its decision to give Manhunt 2 a Mature rating, meaning it is suitable for players 17 years and older.

'Manhunt 2's' rating makes it unmistakable that the game is intended for an older audience. The unauthorized hacking into the code of this game doesn't change that basic fact, ESRB President Patricia Vance said in a statement.

The board initially slapped an Adults Only rating on the title in June, a kiss of death for a game since hardware makers Sony, Microsoft Corp and Nintendo Co Ltd do not allow such content on their machines.

A modified version of the game in which gruesome execution scenes were edited and blurred was given a Mature rating in August, and the game went on sale on Wednesday for Nintendo's Wii console and Sony's PSP and PlayStation 2.

Almost immediately, hackers said they had modified the PSP version of the game to remove the blurring effects.

Manhunt 2 is published by Take-Two Interactive Software Inc, which was embroiled in scandal two years ago after hackers found hidden sex scenes in their hit game Grand Theft Auto: San Andreas, prompting it to get yanked from shelves until the scenes were removed.

Common Sense Media, a group that rates movies, TV shows and other media based on their suitability for children, said it was asking the Federal Trade Commission to look into how the ESRB reduced its rating on Manhunt 2.

The Parents Television Council, which aims to stop TV and other media from targeting children with violent or sexual content, urged the board to reinstate its original Adults Only rating on the game and suspend reviews of other games from Rockstar and Take-Two.

Either the video game industry will step up and do the right thing, or else it will defy the public interest in order to preserve its own economic interest, PTC President Tim Winter said in a statement.

Take-Two Chairman Strauss Zelnick said in a statement the company tried to ensure its games were sold to the appropriate audience.

I urge consumers to respect that commitment and to enjoy our games as they are meant to be played, without modifying or illegally downloading modified copies, he said.

Manhunt 2 launched amid mixed reviews, with the Wii version garnering an average score of 70 on Game Informer magazine gave the game a 78, applauding its uncompromising take on morality and violence, while Web site gave it 40, dismissing it as largely forgettable.