Bitcoin fell to $32,601 at 1800 GMT (2 p.m. ET), losing $4,899.54 from its previous close. It hit a high for the year of $64,895.22 on April 14.
Ether, the coin linked to the ethereum blockchain network, dropped 17% to $1,905 on Sunday, losing $391.31 from its previous close.
Bitcoin markets operate 24/7, setting the stage for price swings at unpredictable hours.
"Many point to bitcoin's volatility as untenable," wrote RBC Capital Markets' Amy Wu Silverman in a research note published on Saturday. "Indeed, Bitcoin makes severe and dizzying swings."
Bitcoin had been under pressure after a series of tweets last week by billionaire Tesla Chief Executive and cryptocurrency backer Elon Musk, chiefly his reversal on Tesla accepting bitcoin as payment.
In addition, on Friday China cracked down on mining and trading of the largest cryptocurrency as part of ongoing efforts to prevent speculative and financial risks.
China's Financial Stability and Development Committee, chaired by Vice Premier Liu He, singled out bitcoin as the asset it needs to regulate more.
The statement, which came days after three Chinese industry bodies tightened a ban on banks and payment companies providing crypto-related services, was a sharp escalation of the country's push to stamp out speculation and fraud in virtual currencies.
China's latest campaign against crypto came after the U.S. Treasury Department on Thursday called for new rules that would require large cryptocurrency transfers to be reported to the Internal Revenue Service, and the Federal Reserve flagged the risks cryptocurrencies posed to financial stability.
(Reporting by Maria Ponnezhath in Bengaluru; Additional reporting by Bhargav Acharya and the Global Finance & Markets Breaking News team; Editing by Lisa Shumaker and Bill Berkrot)