One of Germany's most famous biscuit-makers has appealed to an extortionist dressed as the "Cookie Monster" to return its prized golden biscuit emblem.

The Bahlsen biscuit company's emblem has hung above its headquarters in Hanover since 1913 and was first reported stolen a week ago.

Just days after it went missing a ransom note arrived at the local newspaper which included a photo of the thief dressed as the "Cookie Monster" from children's television series "Sesame Street", pretending to take a bite from the golden biscuit.

In a message posted on Facebook on Thursday and addressed to the monster, Bahlsen promised to donate 52,000 packets of biscuits to charities if the 20 kg (44 pound) golden biscuit was returned.

The original ransom note demanded that Bahlsen give biscuits to children in hospitals across Hanover and donate a 1,000-euro ($1,400) reward for the emblem's return to an animal home.

A spokeswoman denied media suggestions that the theft and ransom note were part of a marketing stunt and said the firm was anxious to recover the emblem as soon as possible.