On Friday, shares of European banking titans plunged, as Deutsche Bank fell 13%, and UBS Group dropped 6%, following investors noting a sharp increase in credit default swaps being recorded Thursday night.

The declines spread to other banks with high exposure to corporate lending, as Commerzbank fell 9% and Societe Generale dropped 7%.

Credit default swaps are a kind of insurance which protect corporate bond holders against a company’s default. On Thursday night they spiked to 173 basis points, up from 142 basis points on Wednesday, marking the highest level since they were introduced in 2019.

Investors have been extremely concerned since the emergency rescue of embattled Swiss lender Credit Suisse, in a government-brokered deal for Swiss banking giant UBS to acquire it. One part of the deal that was struck involved writing-off of $17 billion worth of Credit Suisse’s AT1 bonds. The write-off left the bond-holders empty-handed and highlighted yet another risk for investors involved in the banking sector.

Investor concerns only grew after the US Federal Reserve and the European Central Bank both chose to raise interest rates yet again this week, despite the precarious nature of the banking sector.

In the US, shares of US banking giants like JPMorgan Chase, Wells Fargo and Bank of America fell roughly 2% lower at the start of trading on Friday, as regional lenders, a key focus of investor concerns, were mixed.