The index of top European banks (.SX7P) was down 1% in early trading, with German banking giants Deutsche Bank (DBKGn.DE) and Commerzbank (CBKG.DE) both falling 0.8%. The rescue of Credit Suisse, which followed the collapses of California-based Silicon Valley Bank (SVB) (SIVB.O) and New York-based Signature Bank (SBNY.O) ignited broader concerns about investors' exposure to a fragile banking sector. The decision to prioritise shareholders over Additional Tier 1 (AT1) bondholders rattled the $275 billion AT1 bond market and some Credit Suisse AT1 bondholders are seeking legal advice. "The AT1 instruments issued by Credit Suisse contractually provide that they will be completely written down in a 'viability event', in particular if extraordinary government support is granted," FINMA said. However, some watchers think the banking system is more vulnerable to rumour and rapid moves in an era of widespread social media use, posing a challenge for regulators trying to tamp down instability.

---