Shoppers wrestle over a television on Black Friday at an Asda superstore in Wembley, north London, Nov. 28, 2014. Britain's high streets, malls and online sites were awash with discounts on Friday as more retailers than ever embraced U.S.-style Black Friday promotions, seeking to kickstart trading in the key Christmas period. Reuters

Tensions run high among holiday shoppers, especially when big savings are at stake. Several Black Friday fights broke out Thanksgiving night and early Friday in the U.S. and U.K. as consumers sprang at the opportunity to snag doorbuster deals on everything from TVs to lingerie, once again proving that the busiest shopping day of the year isn’t for wimps.

On Thursday, some consumers got a head start on Black Friday sales, as many retailers have extended their holiday shopping hours into Thanksgiving, a sign of increasing competition. Others remained closed Thanksgiving to give employees a holiday and chose to open early Nov. 28.

An estimated 50 million Americans were expected to begin their holiday shopping on Thanksgiving, according to the International Council for Shopping Centers. Other shoppers chose a different route by going online to find deals, a growing trend among consumers of electronics like tablets and smartphones.

Scuffles occurred among bargain hunters broke out over diminishing supplies of discounted big-ticket and even low-priced items. Oftentimes, law enforcement had to intervene. Police in California responded Thanksgiving night to a fight between two shoppers over a $5 Barbie doll, according to ABC 7. The altercation took place at a Walmart in Norwalk, but no arrests were made.

In Indiana, a man and his girlfriend were arrested on charges of attacking a cop, IndyStar reported. Law enforcement said the man was thrown out of a mall for rowdiness, and then was involved in a fight with another man in the parking lot before punching an off-duty police officer who had asked him to leave. Police in Houston found customers fighting over televisions at a Walmart, according to WGN-TV.

Across the Atlantic, in the U.K. -- where the American Black Friday promotion was recently imported even though Thanksgiving is not even a holiday there -- shoppers were at times equally hostile. Fights resulted in several arrests and injuries, including altercations at a number of Tesco stores across the country. “In the interest of customer safety, a small number of these stores contacted police last night to help control crowds safely and stores are now trading normally,” a Tesco spokesperson said, according to the Independent.

Videos posted Thursday and Friday to social media show just some of the mayhem that is the holiday shopping season. Here is a sampling of Black Friday fight videos from around the Web: