The Scream became an iconic work of art, famous across the world

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Thieves have stolen one of the world's best-known paintings from a gallery in the Norwegian capital, Oslo.

Two men took just 50 seconds to climb a ladder, smash through a window of the National Art Museum in Oslo and cut The Scream, by Edvard Munch, from the wall with wire cutters.

The cutters were left behind along with a short ladder as the men fled with the painting. The entire incident was filmed by security cameras.

The director of the museum, Knut Berg, said, "It is impossible to estimate the value of the painting.

"But it is Norway's most valuable, Munch's most renowned, and it would be impossible to sell."

The museum's alarm went off at 0630 local time (0530 GMT) and a security guard immediately alerted police, who arrived within minutes.

Police officers are searching for a Mercedes car thought to have been used as a getaway vehicle.

The painting was in the gallery as the highlight of a Norwegian Culture Festival staged in connection with the Winter Olympics which start today in Lillehammer.

There is widespread speculation that the theft may have some connection with the Games, possibly as a publicity stunt by campaigners. Art experts believe the painting is so well-known that it is unsaleable.

The museum is facing strong criticism over its security after it was revealed that the masterpiece had been moved from the more secure first floor to the ground floor for the exhibition. It is believed to have been uninsured.

The stolen painting is regarded as the most important of the four versions Edvard Munch painted of The Scream, and was created in 1893 as part of his Frieze of Life series in which sickness, death, anxiety and love are central themes.

The haunting depiction of a skull-like face wide-mouthed in agony and despair before a blood-red sunset has become an icon of human anguish across the world.

Several other Munch paintings have recently been stolen: six years ago, another well-known masterpiece, The Vampire, was stolen from the Munch Museum in Oslo, but was later recovered, as was alithograph, Madonna, which disappeared in 1990.

Another painting, Portrait Study, was taken from the National Art Museum last August and is still missing.

Dr Arpad Pusztai's experiments suggested GM foods damage the immune system

The 20 independent scientists have signed a memorandum in support of Arpad Pusztai who was forced to retire last year over his revelations about the effects of biologically altered potatoes on laboratory rats.

An expert on plant toxins, Dr Pusztai was suspended by the Rowett Research Institute in Aberdeen and did not have his annual contract renewed after he publicised his findings on British television.

Former president of the British Society of Allergy and Environmental Medicine Ronald Finn said: "Dr Pusztai's results at the very least raise the suspicion that genetically modified potatoes may damage the immune system."

He continued: "You can imagine a doomsday scenario. If the immune system of the population was weakened, then the mortality would be increased many, many times."

Dr Pustzai, 68, found the internal organs and immune systems of rats was altered by the presence of an additional gene - responsible for the production of the plant toxin lectin - in the potatoes.

A researcher at the department of pathology at Aberdeen University, Stanley Ewen, has just released details of his own experiments indicating rats fed on GM - or transgenic - potatoes absorbed lectin into their intestines.

Mr Ewen explained: "It may be that in GM food a drug-delivery system has been created, delivering something you didn't want to."

The director of the Rowett Institute, Philip James, has defended his decision to suspend Dr Pusztai saying he had become "muddled" over key aspects of the potato experiments.

He denied he had come under political pressure to dismiss the controversial scientist.

Prime Minister Tony Blair has rejected calls for a moratorium on GM food saying there is a rigorous regulatory process before they reach supermarket shelves in the UK.

lithograph: a print produced by lithography（平板畫，平板印刷）