Robinhood stock trading app restricted transactions for GameStop stock and other Reddit thread r/WallStreetBets stocks Thursday, citing market volatility.

Along with GameStop, AMC ($AMC), Blackberry ($BB), and Nokia ($NOK) are among the stocks restricted, Robinhood notified customers in a blog.

"We continuously monitor the markets and make changes where necessary," Robinhood said in the blog. "In light of recent volatility, we are restricting transactions for certain securities to position closing only."

Robinhood added that it "recently revamped and expanded Robinhood Learn," to to help people "educated themselves, including how to make sense of a volatile market."

The restricted stocks were popular on Reddit r/WallStreetBets stocks, where users banded together to drive up prices of such stocks despite traditional hedge funds that had shorted them, The Verge reported.

Robinhood helped the Reddit users drive the stock prices up since the stock trading app allows amateur investors to trade without fees with a "mission to democratize finance for all."

Market makers like Citadel Securities pay e-brokers like Robinhood to execute customer trades, CNBC previously reported.

As of Wednesday, GameStop, which has struggled in recent years, saw its stock climb nearly 2,000% since the beginning of the year amid the Reddit forum growing to some 3 million people. On Thursday, GameStop was trading at $360 a share compared to $18 a share a few weeks ago.

A WallStreetBets subreddit user called Robinhood's halt on new options or shares "market manipulation," with other similar complaints on the forum.

More than half of Robinhood users own at least some GameStop stock, a popup on the Robinhood app shows.

U.S. Rep. Rashida Tlaib, R-Mich., also voiced concern on her official Twitter account.

"This is beyond absurd," Tlaib tweeted. The House Committee on Financial Service needs "to have a hearing on Robinhood's market manipulation. They're blocking the ability to trade to protect Wall St. Hedge funds, stealing millions of dollars from their users to protect people who've used the stock market as a casino for decades."

Last month the Securities and Exchange Commission fined Robinhood $65 million for misleading customers about how it makes money.

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