Dow dives over 600 points as Credit Suisse selloff injects fresh unease into markets

• US stock futures sank Wednesday as worries about Credit Suisse's financial health revived fears over banks.
• The Swiss bank's shares plunged 22% in Zurich after its top investor ruled out further support.

US stocks looked set to fall at the opening bell Wednesday as a plunge in Swiss banking giant Credit Suisse's share price injected fresh unease into markets.

Dow Jones Industrial Average futures shed as much as 600 points in premarket trading and were down 530 points at last check. S&P 500 futures slumped 1.6%, while Nasdaq Composite futures fell 1.4%.

The drop came after a huge selloff in Credit Suisse shares undermined investor sentiment, with fears growing that the collapse of Silicon Valley Bank will spiral into a full-blown banking crisis.

Credit Suisse's Zurich-listed shares plummeted 22% early Wednesday after its top shareholder the Saudi National Bank ruled out extending any more to support the troubled bank, with trading in the stock being halted several times.

Its American Depositary Receipts had fallen 18.3% to $2.05 at last check.

The extended tumble in Credit Suisse's share price has fueled unease about the global banking sector after SVB, Signature Bank, and Silvergate Capital all imploded over recent days.

"Investors are now trying to guess which might be the next domino to fall, both in the US and outside it," IG Group's chief market analyst Chris Beauchamp said.

"Contagion is on everyone's lips, and at present it is too tough to say whether the crisis can be contained effectively," he added.