The ivory pieces, taken from Sydney L Moss Oriental Art, have a combined value of pounds 156,000. Among the most important are an ivory netsuke of a Shishi, a Buddhist lion dog, and a goat, dating from about 1780 and 1760 respectively.
Douglas Wright, of Sydney L Moss, believes professionals carried out the theft as it took them just two minutes to smash through a strengthened glass door and break into a display-case.
Because most netsuke are no larger than a ping-pong ball, they are relatively easy to smuggle. 'You could walk out of the country with 50,' said Philip Saunders, of Trace magazine, which liaises with the police and art trade in tracking down stolen works of art. Indeed, security reasons force most serious netsuke collectors to keep these tiny treasures (in materials such as ivory, wood, coral, bone and shell) in safes or bank vaults.
In recent years, there has been an increase in the number of thefts of netsuke. The July issue of Trace magazine details 83 Japanese items taken in a burglary in Poole, Dorset.
Mr Wright said: 'Someone's targeting netsuke. It's a new thing . . . suddenly the underworld is awakening. Perhaps because there has been such interest on the legal market.'
Although not discounting the theory of someone stealing-to-order, he added: 'If someone's filthy rich, they can afford to buy netsuke. The dearest netsuke was sold for pounds 125,000 at Sotheby's two years ago.'
The fact that the pieces are well-documented will also make them difficult to sell. 'Unless they've found a buyer who has no scruples as to owning them . . . these pieces will be 'buried' for a while,' Mr Wright said.