The first digital radios priced under £100 are flying off the shelves and demand is now outstripping supply, manufacturers have said.

Pure Digital - which makes the £99 Evoke radios - said the situation could get "problematic" if there were a big increase in demand at Christmas.

Consumers are already struggling to find them in the shops.

Listeners get a greater choice of stations from the BBC and commercial stations, and an end to the kind of interference that can disrupt FM broadcasts.

Up until now, listeners who want to hear stations like the BBC's Five Live Sports Extra and 6 Music, and independents Planet Rock and Oneword, have had either to buy hi-fi tuners for more than £300, or tune in via the internet or digital TV.

Pure Digital is struggling to meet demand for this set

Pure Digital spokesman David Harold said: "The radios are selling extremely quickly. They are certainly not sitting on the shelves.

"It is becoming quite a struggle for us to keep up with the demand."

He added that Pure Digital was shipping "a couple of thousand of the radios every couple of days".

"If things continue this way, we are going to have to up the numbers we order," he said.

"If there is a big surge in demand at Christmas the situation could get problematic.

"We thought the market for this product would grow to be significant but, with an untried product, it is always difficult to know how successful it will be."

Kitten campaign

High Street retailer Argos received 600 inquiries about the Evoke last week, and sold between 330 and 400 sets.

Around 85,000 digital radio sets have been sold so far in the UK, according to the Digital Radio Development Bureau, which markets the technology.

That figure has increased from 50,000 at the start of the year.

Spokeswoman Mandy Green told BBC News Online the organisation is expecting the number to rise to 120,000 by the start of next year with the help of an advertising campaign featuring Atomic Kitten.

Ads for BBC services such as 1Xtra and the Asian Network are also helping to fuel demand for the sets. The corporation's final digital station, BBC7, launches next month.