Shares in Silicon Valley Bank (SVB), a key lender to technology start-ups, has plummeted as investors moved to withdraw their deposits.
The slide came a day after the bank announced a $2.25bn (£1.9bn) share sale to help shore up its finances.
Shares in banks have fallen around the world – with the four largest US banks, including JP Morgan and Wells Fargo, losing more than $50bn in market value.
One venture capitalist told the BBC the day’s events were “wild” and “brutal”.
Stock markets in Asia also fell on Friday, led lower by shares in banks.
Shares in SVB saw their biggest one-day drop on record as they plunged by more than 60% and lost another 20% in after-hours trade.
The firm launched the share sale after losing around $1.8bn when it offloaded a portfolio of assets, mainly US Treasuries.
But more concerningly for the bank, some start-ups who have money deposited have been advised to withdraw funds.
Hannah Chelkowski, founder of Blank Ventures, a fund that invests in financial technology, told the BBC the situation was “wild”. She is advising companies in her portfolio to withdraw funds.
“It’s crazy how it’s just unravelled like this… The interesting thing is that it’s the most start-up friendly bank and supported start-ups so much through Covid. Now VCs are telling their portfolio companies to pull their funds,” she said.
“It’s brutal,” she added.
A crucial lender for early-stage businesses, SVB is the banking partner for nearly half of US venture-backed technology and healthcare companies that listed on stock markets last year.
SVB did not immediately respond to a BBC request for further comment.
In the wider market, there were concerns about the value of bonds held by banks as rising interest rates made those bonds less valuable.
Central banks around the world – including the US Federal Reserve and the Bank of England – have sharply increased interest rates as they try to curb inflation.
Banks tend to hold large portfolios of bonds and as a result are sitting on significant potential losses. The falls in the value of bonds held by banks is not necessarily a problem unless they are forced to sell them.
But, if like Silicon Valley Bank, lenders have to sell the bonds they hold at a loss it could have an impact on their profits.
“The banks are casualties of the hike in interest rates,” Ray Wang, founder and chief executive of Silicon Valley-based consultancy Constellation Research told the BBC.
“Nobody at Silicon Valley Bank and in a lot of places thought that these interest rate hikes would have lasted this long. And I think that’s really what happened. They bet wrong,” he added.