Bitcoin lost 2.1 percent and its biggest rival Ether slumped 8.9 percent while the market capitalisation of digital assets tracked by CoinMarketCap.com shrank to $197bn (£152.36bn) – down about $640bn (£494.99bn) from its January peak.
Cryptocurrencies have been on the slide for five of the past six weeks amid broader concerns the adoption of digital assets is taking longer than anticipated.
These fears intensified when Ether co-founder Vitalik Buterin said the days of explosive growth in the blockchain industry had probably already come and gone.
His comments came over the weekend as the US Securities and Exchange Commission (SEC) stepped in to halt trading in two exchange-traded notes linked to the cryptocurrency.
SEC officials cited a “confusion amongst market participants” based in the US as to the nature of the financial instruments as the reason for the move.
They said their decision was in “the public interest” and that it was line with its mandate to ensure the “protection of investors.”
Ryan Rabaglia, head of trading at cryptocurrency dealing firm OSL in Hong Kong, said: “The temporary suspension of these products led to an initial knee-jerk reaction but ultimately, it’s just another obstacle for the market to overcome.”
Cryptocurrencies remained under pressure as the markets open today despite reports that Citigroup Inc had developed a new mechanism for investing in the space.
Insiders said the US bank plans to act as an agent issuing so-called digital asset receipts, or DARs, to enable trading by proxy without direct ownership of the underlying coins.
The Bloomberg Galaxy Crypto Index of major virtual currencies dropped 4.1 percent to 392.68 at opening in London, heading for its lowest close since mid-November.
Ether fell to $199.05 (£153.95) and Bitcoin slipped to $6,313.51 (£4,883.03).
Ether’s fall has been faster than Bitcoin’s in recent months amid fears blockchain-related firms are cashing out of the number two cryptocurrency.
Mr Rabaglia said: “The rhetoric around ICOs continuing to unload their raise proceeds on the market remains valid.
“It’s hard to see how that story line will go away any time soon.”