ap photo Traders work on the floor at the New York Stock Exchange in New York, Wednesday.

GENEVA — Fears about the world banking system spread to Europe on Wednesday as shares in the globally connected Swiss bank Credit Suisse plunged and dragged down other major European lenders in the wake of bank failures in the United States.

At one point, Credit Suisse shares lost more than a quarter of their value, hitting a record low after the bank’s biggest shareholder — the Saudi National Bank — told news outlets that it would not put more money into the Swiss lender, which was beset by problems long before the U.S. banks collapsed.

The turmoil prompted an automatic pause in trading of Credit Suisse shares on the Swiss market and sent shares of other European banks tumbling, some by double digits. That fanned new fears about the health of financial institutions following the recent collapse of Silicon Valley Bank and Signature Bank in the U.S.

Speaking Wednesday at a financial conference in the Saudi capital of Riyadh, Credit Suisse Chairman Axel Lehmann defended the bank, saying, “We already took the medicine” to reduce risks.

When asked if he would rule out government assistance in the future, he said: “That’s not a topic. … We are regulated. We have strong capital ratios, very strong balance sheet. We are all hands on deck, so that’s not a topic whatsoever.”

But Switzerland’s centtral bank announced late Wednesday that it was prepared to act, saying it would support Credit Suisse if needed. A statement from the bank did not specify whether the support would come in the form of cash or loans or other assistance. At the moment, regulators said, they believe the bank has enough money to meet its obligations.

Credit Suisse then said early Thursday that it is taking measures to shore up its finances, including exercising an option to borrow up to 50 billion francs ($53.7 billion) from the central bank.

“This additional liquidity would support Credit Suisse’s core businesses and clients as Credit Suisse takes the necessary steps to create a simpler and more focused bank built around client needs,” the bank said.

A day earlier, Credit Suisse reported that managers had identified “material weaknesses” in the bank’s internal controls on financial reporting as of the end of last year. That fanned new doubts about the bank’s ability to weather the storm.

Credit Suisse stock dropped about 30%, to about 1.6 Swiss francs ($1.73), before clawing back to a 24% loss at 1.70 francs ($1.83) at the close of trading on the SIX stock exchange. At its lowest, the price was down more than 85% from February 2021.

After the joint announcement from the Swiss National Bank and the Swiss financial markets regulator, the shares also made up some ground on Wall Street.

The stock has suffered a long, sustained decline: In 2007, the bank’s shares traded at more than 80 francs ($86.71) each.

With concerns about the possibility of more hidden trouble in the banking system, investors were quick to sell bank stocks.

France’s Societe Generale SA dropped 12% at one point. France’s BNP Paribas fell more than 10%. Germany’s Deutsche Bank tumbled 8%, and Britain’s Barclays Bank was down nearly 8%. Trading in the two French banks was briefly suspended.

The STOXX Banks index of 21 leading European lenders sagged 8.4% following relative calm in the markets Tuesday.

The turbulence came a day ahead of a meeting by the European Central Bank. President Christine Lagarde said last week, before the U.S. failures, that the bank would “very likely” increase interest rates by a half percentage point to fight against inflation. Markets were watching closely to see if the bank carries through despite the latest turmoil.

Credit Suisse is “a much bigger concern for the global economy” than the midsize U.S. banks that collapsed, said Andrew Kenningham, chief Europe economist for Capital Economics.