A Bitcoin sign is seen at the entrance of a cryptocurrency exchange office on April 16, 2021 in Istanbul, Turkey.

Chris McGrath | Getty Images

Bitcoin’s price fell back below $40,000 level on Friday after Chinese authorities intensified calls to crackdown on mining and trading the cryptocurrency.

The digital coin was last down 7.3% at a price of $37,256.36 by 1:20 p.m. ET, according to Coin Metrics data, on pace for its worst week since March 13. It bounced above the $42,000 mark on Thursday as digital currencies attempted to rebound from a big sell-off earlier in the week.

Other cryptocurrencies were in the red Friday, with ether last down 11.3% at $2,486.34, XRP off by 12.8% at $1.04 and litecoin falling 12.9% to $183.54. Dogecoin, a meme-inspired crypto supported by Tesla CEO Elon Musk, was down 11.3% at 36 cents.

Bitcoin’s gains were capped Friday after the U.S. Treasury Department said a day earlier that it would require any cryptocurrency transfer worth $10,000 or more to be reported to the IRS.

“Cryptocurrency already poses a significant detection problem by facilitating illegal activity broadly including tax evasion,” the Treasury said.

Read more about cryptocurrencies from CNBC Pro