Washington, Nov 26 (IANS) US online sales surged on Black Friday, with Amazon.com Inc offering the steepest discounts among e-commerce sites as it set the agenda for what has traditionally been the biggest shopping day of the year for brick-and-mortar retailers. Though in-store customer traffic picked up in the afternoon, it paled in comparison to the jump in online sales, NBC news cited analysts as saying. Macy's Inc's website crashed as it saw heavy traffic on Friday. It had to delay customers from entering the site at three different times. Online sales on Friday hit $1.70 billion as of 3 p.m., according to Adobe Digital Index, after reaching $1.13 billion on Thursday, up almost 14 per cent from a year ago. The National Retail Federation expects total sales this holiday season to increase by 3.6 per cent to $655.8 billion, mainly due to the rise in online shopping. This weekend's shopping could reflect signs of faster economic growth in the fourth quarter this year. Administrative assistant Kelsey Gilford, 52, was shopping at Chicago's Water Tower mall on Friday but had already made purchases online on Thursday. "I looked at some online deals on J.C. Penney which were good. I bought a small kitchen appliance yesterday (Thursday)," she said. Amazon.com Inc offered a 42 per cent off, compared with 33 per cent off at Walmart, 35 per cent at Target and 36 per cent at Best Buy. Amazon said Black Friday would surpass last year in terms of the number of items ordered on its website. The Seattle-based company declined to provide specifics. Online shopping continued to grow, with Adobe saying that Black Friday was on track to set a new record by surpassing the $3 billion mark for the first time. It is also expected to become the first day in US retail history to drive over a billion dollars from mobile sales. Mobile accounted for 40 per cent of sales, with 29 per cent from smartphones, and 11 per cent for tablets. Combined with Thursday's $1.93 in online sales on Thanksgiving, the two days are expected to close out at nearly $5 billion in sales. Tamara Gaffney, principal analyst and director, Adobe Digital Insights, said: "We expect Cyber Monday to surpass Black Friday and become the largest online sales day in history with $3.36 Billion." Meanwhile, UK shoppers also rushed to buy Black Friday bargains, as retailers and payment firms reported strong sales. Barclaycard said it had seen a record number of transactions on Friday, while Argos, John Lewis and Currys PC World reported a surge in orders, BBC reported. In the UK, analysts expect sales on Friday to have topped last year's 1.9 billion pound, with people hunting for discounts ahead of an expected rise in prices next year. "The Black Friday promotions at the end of November are the start of a longer, more drawn-out peak season, which begins with most of the activity online and then moves in-store as we get closer and closer to Christmas day," said Richard Jenkings, data analyst at credit reference agency Experian.