China’s latest crypto crackdown is hitting operators hard.

At least five exchanges in the country have halted operations or say they will no longer serve domestic users this month, after regulators issued a series of warnings and notices as part of a cleanup of digital currency trading, The Japan Times reported.

China is stepping up scrutiny of its massive cryptocurrency industry just weeks after President Xi Jinping ignited a market frenzy by declaring Beijing’s support for the blockchain technology that underpins the sector.

However, financial watchdogs including the Chinese central bank have in past weeks ordered cryptocurrency firms to shutter and warned investors to be wary of digital currencies, seeking to rein in a market prone to excesses. Weibo, a Chinese Twitter-like service, suspended accounts operated by major exchange Binance Holdings Ltd and blockchain platform Tron.

Taken together, the latest wave of shutdowns and restrictions represent the biggest cleanup of the sector since an initial Chinese clampdown in September 2017. Although exchanges that allow users to buy bitcoin and ether with fiat money were banned, trading had remained rampant in China through over-the-counter platforms or services that deal with cryptocurrency assets only.

Now, even those alternatives have succumbed to regulators, spooking investors. Bitcoin this week sank to its lowest level in six months at the end of its longest losing streak since at least 2010. The largest cryptocurrency recovered with a 6% rebound on Wednesday, but is still poised to post its worst month since November last year.

Twenty of the top 50 exchanges are based in the Asia-Pacific region and accounted for about 40% of bitcoin transactions in the first half of the year, according to data from Chainalysis. Within the region, the most exchanges are in China, the research firm found.

Aaron Hu, a 26-year-old computer engineer in the central Chinese city of Changsha, said he moved all the cryptocurrency he holds – several million yuan’s worth – from exchanges like Binance and OKEx to his own wallet address. “The first thing I thought of is how to secure my assets,” he told The Japan Times.

Exchanges affected

The exchange operators Bitsoda and Akdex ceased operating in China last week. Another exchange platform called Biss paused its services earlier this month to allow its executives to collaborate with the Chinese authorities in an ongoing probe, FXStreet reported.

Another exchange that is  likely to be shut down by the government is Btuex. However, Btuex plans to serve overseas customers in the future. The Idax exchange on Sunday said it was going to lock out all China-based customers.

Katie Talati, head of research at Arca, a Los Angeles-based asset manager that invests in cryptocurrencies, told FxStreet:

“It appears that, like everything else within their borders, China feels it needs to have tighter controls on the crypto market including exchanges, miners and asset issuers.”

She added “I do believe, however, they are moving in a similar direction as Japan and other jurisdictions that have tight and clear regulations for crypto businesses.”