HSBC Holdings has been placed under formal investigation regarding its connections to a Lebanese central bank scandal, according to reports from financial regulators. The investigation represents a significant escalation in scrutiny of the British banking giant's operations in the Middle East region.

Separately, HSBC shares declined following reports of potential restrictions on Hong Kong bank account operations. AIA Group also saw its stock price fall amid the same reports concerning banking curbs in the territory, though specific details of the restrictions were not immediately clear.

The dual pressures on HSBC highlight ongoing regulatory challenges facing major international banks operating across multiple jurisdictions. The Lebanese central bank investigation adds to a series of compliance issues that have affected major financial institutions in recent years.

Meanwhile, in other financial market developments, analysts at various investment banks have been adjusting their outlook on different sectors. Barclays traders have recommended purchasing protection against a potential technology-led pullback in the S&P 500, suggesting some caution in the current market environment despite the ongoing bull run.

The developments come as equity markets face various crosscurrents, with some analysts warning that an anticipated surge in equity issuance could test the durability of the current bull market in US stocks.