Knut fans mourn famous polar bear

Animal lovers have been paying tribute to the world's most famous polar bear after he died suddenly at a German zoo.

Knut became an international star, with his own film and TV show, after being abandoned by his mum in 2006 and hand-reared by keepers at Berlin Zoo.

He died suddenly on Saturday afternoon at the age of four.

Polar bears can live for up to 30 years in captivity, and scientists are now trying to find out why Knut died so unexpectedly.

See pictures of Knut as a cub growing up

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In 2007, Knut is reported to have made more than £4.2m in extra income for Berlin Zoo, from the sale of tickets and Knut merchandise.