Shoppers desperate for bargains caused chaos in Asda stores on Friday as the Walmart-owned supermarket brought the US tradition of Black Friday to Britain.

Customers scrambled and pushed to snatch cut-price electrical goods after queueing for several hours outside Asda stores around the country.

Shoppers took to the social media site Twitter to describe early morning queues and fights. A woman in Merseyside was reportedly taken to hospital in the morning after being assaulted in a queue outside an Asda store. A man was arrested in Bristol after another fracas.

Customers responded to Asda's Black Friday request for photos with a torrent of complaints. Photograph: Twitter

There were similarly frenzied scenes at Asda in Benton, North Tyneside, where some shelves were cleared in minutes as shoppers overran the store. Margaret Green, 55, from North Tyneside, told newswires: "It was bedlam, chaos. It was absolutely jam-packed. There was lots of screaming and shouting. I'm surprised there weren't people on the floor. I found it disgusting. It was horrific."

Asda said it had tried to ensure safety by putting security guards in all its stores. A spokesman said: "This is the first time Black Friday has been done on this scale in stores across the UK and our customers were eager to take advantage of the great offers available to them. We planned for high demand and the half a million Black Friday products on offer to our customers have been selling quickly since 8am." The store group knew certain products would be popular, but "no one expected some of them to be sold out within a few hours", it added.

The US tradition of Black Friday, the day after Thanksgiving when shops cut prices to encourage sales on what is a national holiday on other side of the Atlantic, is gathering pace in the UK. It is being driven by US retailers with a presence in Britain, including Apple, Amazon and Asda.

British retailers, including John Lewis and Dixons, have also begun offering special deals on electrical goods to encourage shoppers to spend early.

Amazon has been offering discounts all week while Asda, owned by the US retailer Walmart, had discounts of up to 70% on products including plasma TVs and tablets.