A “short squeeze” that started on Wall Street swept across the globe on Wednesday, triggering another day of frenetic moves in the share prices of companies with large bets levied against them.

The White House press secretary Jen Psaki said the Biden administration was “monitoring the situation” as shares of companies including GameStop, the hard-hit cinema owner AMC and BlackBerry surged in a volatile day of trading.

The dramatic moves highlight the growing influence of retail traders, who have organised on the message board site Reddit. The group has focused on pushing up stocks that are the subject of large short bets by hedge funds. Their success in rallying the stock price of GameStop has vindicated a group now targeting companies on both sides of the Atlantic.

Stocks such as US home goods retailer Bed Bath & Beyond, Finnish telecoms group Nokia, German pharmaceuticals company Evotec, former Financial Times owner Pearson and Polish games developer CD Projekt rose sharply in intraday trading.

Shares in cinemas group AMC, which earlier this week clinched a rescue financing, rose 301 per cent on Wednesday, while the retailer Express more than tripled in value. GameStop, which has been at the centre of the retail trading bonanza, shot up 135 per cent.

The gains stood in stark contrast to a broad market decline triggered by concerns about the rollout of vaccines and pandemic risks to the economy. The US S&P 500 index and tech-heavy Nasdaq Composite both slid 2.6 per cent.

“It’s like a wolf pack seeking out the weakest member of the herd,” said Steve Sosnick, chief strategist for Interactive Brokers.

The flash rallies prompted TD Ameritrade to put trading restrictions in place for several securities, including GameStop and AMC. The company said the limits could include restricting short sales or requiring 100 per cent margin for certain trades, moves it said would mitigate risks for itself and its clients.

“We made these decisions out of an abundance of caution amid unprecedented market conditions and other factors,” the brokerage said.

The Securities and Exchange Commission said on Wednesday that it was aware of the volatility across equity and options markets and it was “working with our fellow regulators to assess the situation and review the activities of regulated entities, financial intermediaries, and other market participants”.

William Galvin, the Massachusetts secretary of the commonwealth who last month sued the trading platform Robinhood for “gamifying” investing and failing to protect its users, said trading in GameStop should be halted. “At the present time, the best action is to prevent this from being traded,” he told the Financial Times. (Robinhood has denied the allegations in the complaint from the Massachusetts securities division.)

Line chart of Share price performance on January 27, 2021 (%) showing Day traders pump up the value of a handful of stocks

Some of the companies whose shares surged were targets of Melvin Capital, a hedge fund that has been singled out by day traders. Those included Evotec, which was up 9.6 per cent; CD Projekt, which rose 5.3 per cent; and the German battery manufacturer Varta, which rose 12 per cent before trimming its gains to trade up 6.2 per cent.

Melvin on Wednesday revealed it had closed its GameStop position, having sustained a multibillion-dollar loss on its shorts since the start of this year.

Retail investors are using “a tried-and-true hedge fund strategy of swarming crowded trades held by weak-handed investors”, said Andrew Beer, managing member at fund firm Dynamic Beta Investments.

In contrast to the US, which has limited disclosure on short bets, hedge funds and other investors have to disclose when they have shorted more than 0.5 per cent of a company’s stock in the EU and the UK, making it easier to target a fund’s positions.

Melvin’s latest disclosure shows it has bet against more than 6 per cent of Evotec’s shares, making it the largest single wager against a European company by percentage of shares shorted, according to the data provider Breakout Point. The US hedge fund’s bet against Varta is the fifth largest.

The “short squeeze phenomenon fuelled by retail investors’ discussions is spilling over to Europe”, said Ivan Cosovic, founder of Breakout Point. “We are recently detecting some European stocks being touted as ‘the next GameStop’ among retail investors.”

The targeting of hedge funds will be viewed with irony by many financial market insiders, given that such funds are often the protagonists in short selling attacks on troubled companies.

Heavily shorted shares with no link to Melvin also rose on Wednesday. Shares in Pearson, the British education publishing company that is the third-most shorted stock in Europe, according to IHS Markit, climbed 14 per cent to close at its highest level in 16 months. Daniel Sundheim’s New York-based hedge fund D1 Capital Partners, which has also been shorting Varta, has the biggest bet against Pearson, at 3.8 per cent of its share capital.

Line chart of Pearson share price (pence) showing Heavily shorted Pearson feels the squeeze

The real estate company Wereldhave, in which Woodson Capital has disclosed a 4.2 per cent short position and London-based Adelphi has a 3.6 per cent bet, rose about 5 per cent.

Hedge funds in Europe are now fervently scouring lists of most-shorted stocks and message boards such as Reddit for any signs that their short bets could be in trouble.

“Any good hedge fund group will be looking at this,” said the head of one multibillion-dollar European hedge fund group.

One European hedge fund manager who specialises in short selling described the recent stock market rallies as “insane”, but said the elevated share prices of troubled companies would “make a great opportunity” for short sellers that survived the week’s mayhem.

Additional reporting by Patrick Temple-West