The chief surgeon at a hospital treating victims of Norway's camp massacre said the killer used special bullets designed to disintegrate inside the body and cause maximum internal damage.

Dr Colin Poole, head of surgery at Ringriket Hospital in Honefoss north west of Oslo, said surgeons treating 16 gunshot victims have recovered no full bullets.

He said: "These bullets more or less exploded inside the body. ... These bullets inflicted internal damage that's absolutely horrible."

Ballistics experts say so-called dum-dum bullets also are lighter in weight and can be fired with greater accuracy over varying distances. They commonly are used by air marshals and hunters of small animals.

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