He has been playing war games for six months, he said, and found Lee on Uwants, an online marketplace.

After confirming the sale online, they arranged to meet at Prince Edward to complete the transaction.

Cheung paid HK$300 for the gun, which he said would have cost HK$570 in a store. 'This is my first time buying from Simon, but I actually have two other purchases I'm going to pick up in the station tonight,' said Cheung.

About 50 other people milled around the edges of the station's fare-paid zone, most of them waiting to pick up goods they had ordered on the internet.

Cash changed hands for make-up kits, concert tickets, cameras and clothing.

In most parts of the world, online shopping is a straightforward process. You find what you want, enter your credit card information and have it shipped to your home.

Not so in Hong Kong, where analysts describe the online retail market as 'underdeveloped' and consumers have long been sceptical of online purchasing.

Here, consumers treat the internet like a giant catalogue, scouring the Web for bargains before venturing out into the real world to actually buy the goods.

Vendors advertise products on sites like Uwants and Yahoo Auctions, which function like online bazaars where shoppers can browse for products, compare prices and, in many cases, negotiate with vendors.

Rather than risk receiving a dud product in the mail, shoppers walk to the nearest MTR station to pick up their purchases.

At the busiest time for exchanges, which is usually in the early evening after people get off work, some MTR stations take on the appearance of miniature marketplaces.

'I like to be able to see what I'm buying before I pay for it and I also like to talk about it,' said Amanda Chan, 39, who was spotted at Prince Edward MTR buying a make-up kit. She spent nearly 20 minutes chatting with the vendor. 'She brought me a bunch of different products to sample,' said Chan.

The diversity of products available online is what appeals to Tam Yik-yan, 26, who started shopping on Yahoo Auctions last year.

'There aren't a lot of well-priced second-hand stores in Hong Kong, at least not in a cluster where I can just browse at different places,' she said. 'And I can shop while I'm at work.'

Online shopping has another big draw - it's cheap. Penne Chong, 27, works as a sales clerk at a Cheung Sha Wan jewellery store and sells her shop's necklaces on Yahoo Auctions.

Because she is able to buy the products with an employee discount, her customers end up paying less than half the retail price.

Though Chong would prefer saving time by shipping the goods to her customers, most request to collect them in person.

'People are afraid to buy things online. They think the vendor might take the money without sending the product,' she said. 'I'll go meet them as long as I don't have to leave the MTR station, so I don't have to pay much for transport.'

Thanks to that kind of flexibility, online markets are doing well in Hong Kong even as conventional online retailing struggles to gain a foothold. But sites that blend online and offline shopping are thriving.

In 2007, Yahoo Auctions was doing so poorly in most parts of the world that it shut all of its sites down, except those in Hong Kong, Taiwan and Japan.

The volume of transactions on Yahoo Auction's Hong Kong site has since grown 20 per cent a year.

More than 800,000 items are available for purchase on the site and the total value of its transactions reached HK$78 million in October.

It earns money through advertising and by charging vendors between HK$1 and $4 to post their item online.

Yahoo Auctions encourages first-time shoppers to meet vendors in person, said Jeff Yeung, the firm's director of product management.

'Meeting face-to-face for item delivery allows the buyer to inspect the quality of the item before accepting it, lower mailing costs and avoid the risk of misdelivery,' he said.

That doesn't sit well with the MTR, which recently put notices in stations warning passengers it is forbidden to 'carry out any type of business activity or trade' in the station.

It was also forbidden to 'pass, push or throw any matter or thing between the paid and unpaid areas'. The 'problem' is most severe at Lo Wu, Sheung Shui and Fanling stations on the East Rail Line, where the exchange of goods has been 'adversely affecting passenger flow', according to MTR spokesman Jason Chan Lap-yan.

But a crackdown at urban stations, where most online shopping exchanges occur, doesn't seem to be on the agenda.

At Prince Edward, despite the rush-hour crowds, MTR employees and police officers turned a blind eye to the transactions taking place.

Baniel Cheung Tin-sau, a marketing consultant and lecturer in the University of Hong Kong's faculty of business and economics, said: 'People enjoy the social interaction of shopping. It's a chance to spend time with friends, which is why many people like to buy things offline.'

'People in the rest of the world now download software from the internet, but people herestill go to shops to buy it on CDs, in boxes.'