Rosie the rhinoceros took her last breath somewhere on the Indian subcontinent early last century. She was shot, skinned, stuffed and shipped to London. Then, in 1907, she was acquired by Ipswich Museum, which swapped her with the Natural History Museum for a pig. For more than a century, in Ipswich, she has suffered the pats of generations of school children, her horn curling to the ceiling.

Last month, however, Rosie suffered the second violation of her ignominious afterlife, almost as cruel as the first.

At 12.27am on Thursday 28 July, two men forced their way through a fire escape at the rear of the museum and made straight for the rhinoceros, where they swiftly wrenched off her 45cm (18-inch) horn. They paused only to collect the skull of a second black rhino, displayed on a ledge above its stuffed cousin, before fleeing in a silver saloon car. Nothing else was stolen.

One might think that only a foolish criminal would bypass the lavish gold burial masks of Titos Flavios Demetrios upstairs in the Egyptian gallery, or even the priceless Hawaiian cape made from feathers of the 'o'o bird, in favour of some century-old rhino remains. In fact, police believe these were very canny criminals indeed.

The Ipswich rhinoceros-horn theft is merely the latest from museums and auction houses across Britain and Europe, driven by soaring prices for horn in the far east. According to Europol, many of them are conducted by an Irish crime gang more accustomed to drug trafficking, money laundering and smuggling.

In February, the stuffed and mounted head of a black rhino was taken from Sworders Fine Art Auctioneers in Stansted Mountfitchet, Essex. On 27 May, a similar head was taken from the Educational Museum in Haslemere, Surrey, which has one of the largest natural history collections in the UK. Last month it was the turn of a museum in Liège, Belgium; three weeks later the Royal Belgian Institute for Natural Sciences in Brussels suffered a similar heist, in which the head of a black rhino, dating from 1827, was stolen.

According to the Metropolitan police, 20 thefts have taken place across Europe in the past six months – in Portugal, France, Germany, the Czech Republic, Belgium and Sweden as well as the UK. Scotland Yard and Europol are now advising galleries and collectors to consider locking up their rhino horn collections or keeping them away from public view. Several institutions, including the Natural History Museum and the Horniman Museum in south London, have removed their displays or replaced horns with replicas.

Behind the crime wave is a surge in demand from the far east and European Asian communities for powdered rhino horn, which is used in traditional Chinese medicines. It is valued as a remedy for everything from fevers and headaches to cancer, and demand is so intense it has pushed the value of horn to £60,000 per kilogram – twice the value of gold. Sworders had valued their rhino head, as an artefact, at £50,000; in the medicinal market, however, it could be worth £200,000.

"It is a new crime phenomenon targeting people who may not have ordinarily been victims of crime and who are vulnerable victims," said Patric Byrne, Europol's head of unit for organised crime networks. "And we are not dealing with petty criminals." The gang "of Irish ethnic origin", which the agency has identified as being responsible for many of the attacks, has a background in violence, drug trafficking and intimidation, he said. "There is a strange and very lucrative market in Chinese medicine. They have found that this product attracts a particular premium in some Asian communities."

Detective Constable Ian Lawson, from the Metropolitan police's art and antiques unit, said the gang used a variety of methods to steal the objects, from carefully planned burglaries to "smash and grab" raids, and police had also been alerted to "hostile reconnaissance" from gang members.

Even more worrying is an associated growth in the poaching of live rhinos, according to conservation experts. "In the last three years, 800 African rhinos have been killed and experts agree that we are facing the worst rhino-poaching crisis in decades," said Lucy Boddam-Whetham, the acting director of Save the Rhino International.

Nearly 200 rhinos were killed in South Africa in the first six months of this year, compared with 125 in the same period last year. The organisation says the museum thefts are stimulating the live-rhino poaching, making their situation even more perilous. There are only 20,000 white rhinos and fewer than 5,000 black rhinos in the wild.

Police tape has been removed from around Rosie at Ipswich Museum, replaced by an apologetic laminated note explaining the missing horn. "People love this museum. It's just so sad," said Bryony Rudkin, the councillor who holds the portfolio for museums and culture at Ipswich borough council. "On the morning after it happened, we had a family come in – a grandmother, mother and child – and the grandmother said, 'I remember coming when I was a child. It's really sad, because everyone in Ipswich knows who she is.'"

"It's a bit selfish to just take the horn," said Miriam Kendall, 10, from Dennington, visiting with her father and younger brother. Tristan, six, thought the thieves were "stupid".

At least there is some good news for Rosie. As a result of the robbery, she is to be the focus of a panel on a new civic mural to be mounted on the town's waterfront, where she will appear not in her mutilated state but with her dignity, and horn, restored. The museum is, meanwhile, making her a replica horn, which will be screwed, very firmly, into the nose of the long-dead beast.