Apple's iPad 2 is already in short supply across the UK just days after going on sale.

Demand for Apple's second-generation tablet computer was always expected to outstrip supply, but few people expected reserves to run dry after one weekend.

Apple stores in London, where queues for the iPad 2 surpassed those for last year's launch, have urged customers to reserve a device online to avoid disappointment.

Argos, the largest non-Apple store to sell the device, confirmed to the Guardian that its 750 outlets in the UK and Ireland have run out of stock. Argos doesn't expect to receive further supplies until 25 April.

"Demand for the next generation iPad 2 has been amazing. We are working hard to get iPad 2 into the hands of every customer who wants one as quickly as possible," Apple said in a statement.

Despite requesting larger quantities, non-Apple retailers including T-Mobile and Vodafone were allocated only around 20,000 devices, meaning supplies were always going to be short. In the US, between 500,000 and 1m iPad 2s were sold in the first weekend when it went on sale a fortnight ago.

T-Mobile and Orange are selling the 16GB Wi-Fi and 3G model for £199 with a 24-month contract for existing customers, or £229 and 24-month contract to new customers.

Vodafone has similar pricing plans, though it is offering all of the storage sizes – 16GB, 32GB and 64GB – in the 3G range, for prices varying from £199 to £349 for existing customers, and £24.50 per month. New customers will have to pay slightly more.

Thousands of shoppers are thought to have queued outside Apple stores in the UK when the iPad 2 went on sale on Friday.