Funny, chilling and provocative, "Bowling for Columbine" is a documentary that works as a hugely entertaining movie, as well as a double-barreled blast at American gun culture and the media.

It starts with tubby, bear-faced American satirist Michael Moore opening a bank account and receiving a rifle as a free gift. Unbelievable, but not the only shocking element in this powerful exploration of violence in the USA.

Moore's inquiries into why America is such a violent society are sparked by the Columbine massacre - the 1999 high school shooting in which 13 people were killed by two malcontent teens who then took their own lives.

At first, it seems his answer will be obvious: readily available guns. But what appears to be a simplistic anti-gun polemic broadens in scope, to tar the media, racism, greed and US foreign policy.

Could it be, he argues, that the public is affected by a violent, interventionist state and the "if it bleeds, it leads" attitude of the news media, rather than video games and rock music?

Moore's left-wing bias is obvious, but "Bowling for Columbine" is no exercise in pious liberal handwringing. The director/star is a plain-speaking, sharp-witted everyman, who isn't looking to score cheap political points, but is infused with a spirit of honest inquiry.

He's been accused of manipulation, but filmmaking is manipulation. And there's no twisting the words of Charlton Heston, when the head of the hugely influential National Rifle Association limply ascribes the murder rate to "mixed ethnicity" and America's "history of violence".

This is a bold, blackly comic masterpiece - everyone should see it.