Grand Theft Auto IV is expected to sell six million copies in a week
Highly anticipated video game Grand Theft Auto (GTA) IV has received a string of near-perfect reviews ahead of its worldwide release.
The game is expected to break records for the fastest-selling game of all time and many shops opened their doors at midnight for gamers.
The game has been classified as 18 in the UK and Mature for US gamers.
US regulators have reminded parents that the title is not designed for children under 17 years old.
In the UK, 41 shops are understood to have put the game on sale at midnight, including outlets in Stevenage, Hertfordshire; Milton Keynes, Buckinghamshire; Hammersmith, in west London; and Bluewater Shopping Centre in Kent.
Reviews for Grand Theft Auto IV have been unanimous in their praise.
UK-based games website Eurogamer called it "game of the year" and handed it a 10 out of 10 review score, while the New York Times said it delivered a "new level of depth for an interactive entertainment experience".
One gamer plays Grand Theft Auto IV
In a joint statement the ESRB and the National Institute on Media and the Family urged parents to check ratings on games for their children.
It said: "With the latest instalment of the Grand Theft Auto series... parents need to be reminded to make sure their kids are playing games appropriate for their age and level of maturity.
"It is critical that parents consider the assigned rating carefully."
The GTA series has proved incredibly popular and almost equally controversial in the last few years.
Analysts predict the game, in which your character Nikko aims to survive the mean streets of a fictional New York, will top last year's record-breaking $300m first-week sales of first-person shooter Halo 3.
The game's launch has also been notable for the lack of marketing hype, with a limited series of TV spots and advertising hoardings.
"Rockstar wants to control the message all the time," Sam Kennedy, editorial director for gaming site 1UP.com, told AP news agency.
"They want this to be seen and perceived exactly the way they want. That's why, outside of the official trailers they released, people haven't seen a lot of gameplay footage in advance of GTA IV shipping.
"They want to build that hype."
Cultural events which hit the mainstream are pretty rare in gaming, which makes Grand Theft Auto's release all the more important
Darren Waters, Technology editor, BBC News website
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