Cryptocurrency miners have halted their China operations after Beijing intensified a crackdown on bitcoin mining and trading.

The crackdown is part of China’s drive to curb speculative crypto trading.

A State Council committee led by Vice Premier Liu He announced the crackdown late on Friday as part of efforts to fend off financial risks.

It was the first time the council has targeted virtual currency mining, a significant business in China that accounts for as much as 70% of the world’s crypto supply.

Cryptocurrency exchange Huobi on Monday suspended both crypto-mining and trading services to mainland Chinese clients, adding it will instead focus on overseas businesses.

BTC.TOP, a crypto mining pool, also announced the suspension of its China business citing regulatory risks, while crypto miner HashCow said it would halt buying new bitcoin rigs.

Crypto miners use increasingly powerful, specially-designed computer equipment, or rigs, to verify virtual coin transactions in a process which produces newly minted crypto currencies such as bitcoin.

The latest shakeout in digital currencies also stems from tighter scrutiny in the United States.

Last Thursday, US Federal Reserve Chairman Jerome Powell said they pose risks to financial stability, and indicating that greater regulation of the increasingly popular electronic currency may be warranted.