The virtual pet that provides companionship at a stroke

It is a pet which needs tender- loving care, constant feeding and strong discipline but it can fit in your pocket and doesn't need taking for walks.

This week sees the inevitable conclusion to our fast-moving, convenience- obsessed world. The cyberpet - a pocket-size chick which has taken Japan by storm - will be launched tonight, and be available in the shops from next Monday.

Nearly 4 million "Tamagotchi", or " loveable eggs", have been sold in Japan to date and the manufacturer, Bandai, plans to sell 13 million over the next year.

The toy looks like an egg-shaped key ring but has a virtual reality chicken, represented as an animated line drawing on a small LCD screen. It may be a virtual pet, but its makers say the creature requires as much attention from its owner as the average cat or dog.

Invented last year by a Japanese housewife, Aki Maita, it imposes a hard regime on its owner, demanding to be virtually fed, virtually exercised and virtually amused by emitting a variety of electronic sounds. It even requires cleaning up after virtually relieving itself. The creature begins life as a Bebitchi ("Babesy"); the aim is to keep it alive for as long as possible, watching it grow through various stages of life right to maturity as an Oyajitchi ("Grampsy"). A Tamagotchi lives for between 10 and 30 days.When its time is up the chicken icon transforms itself into an angel.

The toy - full name "Hyper Interactive Digital Pet Tamagotchi" - squeaks with delight when fed by the press of a button, or when its owner plays peek-a-boo with it. But it also warns the owner when it has defecated and when it is naughty another button can be used to provide discipline.

Although the toy was initially marketed at schoolgirls and working women, Japanese businessmen have been seen caring for their pets on the subway. Bandai say that Tamagotchi creches have been set up in Tokyo to let high- flyers leave their pets under supervision and bereavement counsellors are even being asked to help people through the unexpected passing of their pet.

Two books of advice on caring for the tamagotchi have already been published and the demand is creating a new breed of Tamagotchi criminals. The pet will retail for pounds 10.99 here - but in Japan Tamagotchis are selling for up to 10 times their value on the black market.

So seriously are cyberpets taken in Japan that in Tokyo earlier this year a helicopter, several patrol cars, and a dozen police officers were involved in the pursuit of members of a gang who had made off with a Tamagotchi. The four thieves turned out to be 14 years-old.