Retailers at Essex shopping centre Lakeside have been put on riot alert after the unprecedented popularity of a new text message promotions service called ZagMe.

"It's a lot of fun," said Bill Green, chief executive officer of ZagMe, who said users had been racing around Lakeside to make the most of the free promotions.

The service, which went on trial at the shopping centre last weekend, allowed retailers to message consumers via mobile phones as soon as they arrived in the shopping centre.

According to Mr Green, there were mini-stampedes after one store offered free gifts to anyone who arrived in the shop within half-an-hour.

"I'm blown away by the response. It's way ahead of our expectations. People love it and retailers are enjoying it as they've already seen it's a powerful mechanism to channel people into stores with simple loss-leaders," he added.

Mr Green said that one promotion involving a text message offering free CDs to the first 10 people to make it to the ZagMe stand created something of a riot.

He said ZagMe was signing up 500 users a day and after just four days already had more than 2,000 people using the service.

"We haven't even had the viral effect kick in yet. Once people start telling friends, we expect to take off exponentially."