Police in London, England, have been called to a number of stores, after staff feared that surging crowds of Black Friday shoppers gathering outside could present safety issues.

Staff and shoppers waiting outside four separate stores, three branches of supermarket Tesco, and a branch of supermarket Asda, placed calls to police expressing their concerns, according to a BBC report. The police made no arrests, and no one was injured, the BBC said, but there were reports of massive crowds gathering outside many large stores in the UK, and of fights breaking out as British shoppers scrambled for heavily discounted items such as televisions.

Websites of several UK retailers offering online Black Friday deals had crashed due to high traffic, according to Mail Online. Videos posted online show UK shoppers engaged in scenes familiar to U.S. Black Friday veterans, including shoppers resorting to violence in the scramble for bargains.

While such scenes are a familiar site in the U.S., Black Friday is a comparatively new phenomenon in the UK. Online retail giant Amazon first introduced Black Friday sales to the country, which does not celebrate Thanksgiving, in 2010. Last year, however, was the first time that major UK retailers, including department store chain John Lewis, electronic retail chain Dixons and Walmart's Asda supermarket participated in a serious way, according to Reuters

In 2014, they are being joined by retail giants Sainsburys and Tesco, Apple, Amazon and a whole host of other brands, who are offering shoppers both in-store and online discounts.

According to an estimate by credit card company Visa, UK Black Friday spending in 2014 will be up 22 percent over the previous year. A survey carried out by Barclays found that 65 percent of UK retailers would be participating in Black Friday in some way, according to the BBC.

Traditionally, the UK's busiest retail sales season falls after Christmas, when retailers typically heavily discount huge amounts of stock. And, despite surging crowds at supermarkets, the advent of Black Friday in Britain has not proven to be universally popular, with some users on social media seemingly viewing it as an unwelcome U.S. cultural import.

While Black Friday is finding increasing acceptance in the UK, it appears that continental Europe will prove a harder sell.

Elizabetta Camilleri, CEO of SalesGossip, a web service that tracks discounts at fashion labels across Europe, told Time: “We’ve seen no sign of it happening in France or Spain,” adding that when she asked a German retailer if they might consider a Black Friday sale, the retailer replied, “We are not Americans.”