Internet sales on Black Friday, the day after Thanksgiving, surged faster than expected, according to surveys. They totalled $816m (£524m), a 2 per cent gain on last year, according to Comscore, an analytics company.

Black Friday is marked by increases in sales as many retailers offer discounts to mark the start of the christmas shopping season.

Of the many sites visited by the 50 million Americans on Friday, Amazon was the most popular retailer, with 50 per cent more visitors than any other destination. Apple, Best buy, Target and Wallmart were next on the list, according to Comscore.

"Despite some analysts' predictions that the flurry of brick-and-mortar retailers opening their doors early for Black Friday would pull dollars from online retail, we still saw a banner day for e-commerce,"Comscore's chairman, Gian Fulgoni told the BBC. [2]

IBM Coremetrics, which put the increase at 24 per cent said there was a trend towards shopping on smart phones and tablets.

Purchases made on mobile devices accounted for 9.8 per cent of all online sales, compared to 3.2 per cent last year, and Apple's iphone and ipad generated double the traffic originating from Google's Android system devices, according to the company.

But the sales are expected to increase today-referred to as Cyber Monday- in what many experts believe will be the busiest online shopping day of the year in the US.

A survey commissioned by the US National Retail Federation predicts 123 million Americans are planning to make an online purchase today, a 15 per cent increase on last year.

Mobile devices are expected to be used by 17.8 million Americans today for shopping, almost five times the number used in 2009.

UK companies said they were less clear on when the busiest online shopping day will be.

A spokesman for Intercative Media in Retail group (IMRG), told the BBC that over the last couple of years the compnay noticed a peak of online shopping activity over the period of the next fortnight. He said he expected £3.72 bn will be spent online during this period.

Visa Europe exects today to be the busiest shopping day, with £303m spent online, eBay's forecast is that this Sunday will be its busiest day, with more than 5.5 million people expected to log onto its UK site, and Amazon said it expected a peak the following day.