World's favourite polar bear dies suddenly at Berlin zoo

Knut, who was raised by humans and became a star attraction at the German zoo, died suddenly while hundreds of shocked visitors looked on.

Mourners gathered at the zoo last night with Berlin's mayor calling the death "awful".

The four-year-old shot to fame after his keepers were forced to raise him after he was rejected by his mother after being born into captivity.

Since he was unveiled at Berlin zoo, attendance at the zoo has doubled, according to officials.

He was considered of such high worth to his Berlin owners that they paid another zoo 430,000 to end a legal dispute over ownership.

Knut even featured on the front page of Vanity Fair in 2007, posing with Leonardo DiCaprio in a picture shot by celebrated photographer Annie Leibovitz.

Polar Bears have a life expectancy of between 15 and 20 years in the wild and can live longer in captivity.

Heiner Kloes, a bear keeper at the zoo, said: "It was a completely normal day. He was with the female bears before, who had just been shut away. Then Knut strolled around the enclosure, went into the water, had a short spasm and died."

As many as 700 visitors were at the compound when Knut died, officials said. One visitor said the polar bear had been lying motionless with only his back showing for ten minutes before his compound was fenced off by zoo staff.

Another on-looker, 30-year-old Italian Camilla Verde, said: "Everyone was asking, why is Knut not moving?

"All the zoo keepers who put up the fences were so very sad. One of the said, 'He was our baby'."

Berlin's Mayor, Klaus Wowereit, said "We all held him so dear. He was the star of the Berlin zoos."

Though exact numbers have never been released, Knut merchandise is believed to have brought in hundreds of thousands of euros to the zoo.

A post-mortem will be carried out tomorrow in an attempt to establish the exact cause of death.