Male shoppers erupt into violent brawl in Black Friday chaos

Video has emerged of bargain-crazed shoppers descending into scenes of scrambling brawls as America's famed Black Friday sales kick off after the Thanksgiving holiday.

The video, uploaded to Twitter, shows two men circling each other ready to fight as crowds of dozens wait for shops to open in Kentucky.

The two men start wrestling violently on the ground in the mall's food court as onlookers scream in fear for them to stop.

Two men start to fight in a shopping centre in the US during Black Friday sales. Photo: Twitter/Kody Oliva

The men roll around on the floor as dozens of people crowd around in the shopping mall, screaming for them to stop. Photo: Twitter/Kody Oliva

Security eventually intervened to break up the fight, but not before several punches were thrown.

It's not clear what started the fight.

On Black Friday, the day after the Thanksgiving Day holiday, retailers trumpet special deals that kick off the year-end holiday shopping season.

Photo: Twitter/Kody Oliva

Photo: Twitter/Kody Oliva

Nearly 136 million shoppers are expected to flock to US sales over the Black Friday weekend, both in stores and online, according to the National Retail Federation.

The origins of the name are unclear, with some saying it refers to the intense jams of shoppers.

But the more common explanation is that it points to profits being "in the black" as retailers bank on year-end sales for a large part of their annual profits.

With the boom of online shopping, bricks-and-mortar stores are also beefing up their offers on websites and mobile devices.

Digital research firm comScore predicts online sales in the November-December period will increase 14 percent this year to $70 billion. Another firm, Forrester Research, estimates an 11 percent rise to $95 billion.

Black Friday is followed by Cyber Monday, when back-to-work consumers continue their shopping online. According to the NRF, 184 million people intend to shop online that day.

Retail spending is part of the consumer spending that drives about 70 percent of US economic activity, and so is seen as an indicator of the strength of consumer demand. But the importance of Black Friday has faded somewhat in recent years as shopping trends change and online sales gain.

"Over the past several years, retailers have begun their holiday price promotions progressively sooner, not waiting for the traditional Black Friday day to begin offering price discounts," said Chris Christopher, director of consumer economics at IHS Global Insight.

Many retailers open their doors on Thanksgiving Day, also known as Gray Thursday, cannibalising Black Friday sales, he noted.

This year, the Black Friday sales come in the context of weak retail revenues blamed in part on relatively warm weather that has discouraged cold-weather purchases.

On Wall Street, most major retailers were trading lower in the morning, including Wal-Mart, Amazon, Macy's and The Gap.