In a blog post Monday, Celsius Network said it had frozen withdrawals, as well as transfers between accounts, "to stabilise liquidity and operations while we take steps to preserve and protect assets."
"We are taking this action today to put Celsius in a better position to honour, over time, its withdrawal obligations."
The largest cryptocurrency bitcoin fell further after Celsius's announcement, dropping more than 7.8% to $24,502, its lowest since December 2020.
Ether , the second largest token, dropped as much as 12% to $1,245, its lowest since March 2021.
Celsius Network offers interest-bearing products to customers who deposit their cryptocurrencies with the company, and lends out crypto currencies to earn a return.
It raised $750 million in funding late in November from investors, including Canada's second-largest pension fund. The company was valued at the time at $3.25 billion.
The Celsius move puts the spotlight on the sustainability of crypto lending firms after a period of breakneck growth last year fueled by low interest rates and booming crypto markets.
The surge of interest in crypto lending led to concerns from regulators, especially in the United States, who are worried about investor protections and systemic risks.
Crypto markets have come under pressure alongside stocks and other assets in financial markets amid rising interest rates and surging inflation. The collapse in May of the so-called stablecoin terraUSD and its sister token luna has also shaken the crypto industry.
CEO Alex Mashinsky was quoted in October last year saying Celsius had more than $25 billion in assets.
Mashinsky did not immediately respond to a text message seeking comment outside U.S. business hours.
In a tweet on Monday, rival crypto lender Nexo said it had offered unspecified help to Celsius, but was refused. It said it was "putting together an offer" for any assets.
The company's website on Monday was offering interest rates of up to 18.6%.
In Africa, the Central African Republic recently announced that it was adding cryptocurrencies to its exchange reserves portfolio, a move that international bodies criticized as unwise considering the volatility of cryptocurrency markets.