More than one reviewer has simply described it as 'that scene'. In German, it's known as the 'Flughafen Massaker'. Keith Vaz isn't happy about it, and The Daily Mail is in a predictable lather about 'the game that allows players to massacre civilians'.

As you've probably guessed, I'm referring to Modern Warfare 2, and specifically the airport mission, which Infinity Ward call 'No Russian' (a title which, judging by the speed your character walks, could be a particularly dark pun). In it, you're witness to a brutal slaying of citizens at a Moscow airport; playing the part of an undercover operative infiltrating a group of terrorists, you're forced to wander around the airport lounge as the atrocity unfolds all around you.

What's disturbing about the scene, apart from the blood curdling screams and icy brutality, is that you can choose to join in, gunning down men and women as they run in blind panic. It's intensely disquieting stuff, but taken in the context of the game's narrative, has the requisite effect: it portrays the terrorists as utterly ruthless and entirely deserving of the bullet-ridden justice they'll inevitably receive before the conclusion.

Of course, the Call Of Duty games have always straddled a  rather uncomfortable line between depicting the horrors of war and providing an entertaining shooting gallery, and the morality of depicting realistic violence and warfare in videogames is a constant source of debate - a debate that I won't get into here.

What does interest me is Infinity Ward's decision to make Modern Warfare 2's fourth mission an interactive one rather than a simple cut-scene. I assume their intention was to emotionally invest the player in the atrocity rather than allow them to passively stand by, to implicate them in the violence rather than allow them to act as a voyeur.

I wonder how many players, when they first encountered that scene, were surprised to discover that they could move and fire, and how many, perhaps reluctantly, opened fire on the unsuspecting civilians, if only to see what happened? Of those, I wonder how many felt a pang of guilt afterwards?

The scene reminds me of Bullfrog's nineties classic Syndicate, a sort of real-time strategy game that doubled as a proto sandbox shooter: roaming around a future city, you could steal cars, blow up trains and generally cause as much havoc as you liked. One particular mission saw your quartet of cyborgs faced with the task of assassinating some hapless NPC as he stood apparently giving a speech to a crowd gathered on the steps of a government building.

While it was possible to simply guide your assassins through the throng and take the target down with a single bullet, it was also possible (and quicker) to arm your cyborgs with gattling guns and kill everyone in a hail of bullets. On paper, this virtual atrocity may sound to some like something only a complete sociopath would commit, but I suspect everyone who's played Syndicate will have done this at least once (and probably a dozen times), maybe with a hint of guilt, though probably with a larger helping of glee.

But MW2's No Russian scene takes the first-person shooter into strange new territory; it's an intense, horrifying moment made worse by the realistic screams of fear and anguish. One thing's for sure, there's no glee to be found here.

If the FPS genre was once a digital version of a shoot-the-tin-ducks sideshow at a funfair, the ducks are no longer tin. They've got feathers and bleed profusely once shot. In a game that's otherwise a slam-bang explosion-a-minute Hollywood action epic, No Russian provides an abrupt and singularly disquieting moment that is quite new in gaming, and one that's both disturbing and thought provoking at the same time.

Times columnist AA Gill recently got into trouble for shooting a baboon in Tanzania. His motive? "To see what it would be like to kill someone.

"You see it in all those films: guns and bodies, barely a close-up of reflection or doubt," he wrote. "What does it really feel like to shoot someone, or someone's close relative?"

If it's reflection and doubt Mr Gill wants, I suggest he puts the monkeys aside and buys himself a copy of Modern Warfare 2...

Ryan writes his gaming column every week at Den Of Geek. Last week's is here.