Services like deposits and withdrawals, cheque clearing and instrument issuance are expected to be impacted further owing to the day-long strike.
Netbanking services, however, are least likely to be affected. The Reserve Bank of India (RBI) has already made online NEFT transfers a round-the-clock process and also waived off charges.
ATM services may also be affected at some places.
State-run State Bank of India (SBI), India's largest lender, had earlier said it expects only minimal impact on its services due to the strike as only a few of its employees are members of the striking unions.
Other major state-run banks like the Bank of Baroda have warned of operations getting affected at both its branches and offices.
Ten central trade unions on Monday said around 25 crore people will participate in a nationwide strike on January 8 to protest against the government's "anti-people" policies.
Trade unions - INTUC, AITUC, HMS, CITU, AIUTUC, TUCC, SEWA, AICCTU, LPF, UTUC - along with various sectoral federations and associations had adopted a declaration in September last to go on a nationwide strike on January 8, 2020.
In Chennai, the All India Bank Employees Association (AIBEA) president C. Venkatachalam is leading the strike, an association official said.
Bank unions are joining the CITU-called strike not just in solidarity with their counterparts in other sectors but also to protest against banking reforms and mega merger of public sector banks (PSBs).
They are also demanding a pay hike besides a uniform 5-day week. The demands include a halt in the merger process of 12 PSBs, stopping disinvestment and strategic sales of the central public sector units and a bar on employing contract workers for "perennial nature of work".
Various bank employee associations, including the AIBEA, All India Bank Officers' Association (AIBOA), Bank Employees Federation of India (BEFI), Indian National Bank Employees' Federation (INBEF), Indian National Bank Officers Congress (INBOC) and Bank Karmachari Sena Mahasangh (BKSM) have joined the strike, thereby affecting ATM and branch services.
Several banks have already informed stock exchanges about the strike and its likely impact on banking services.
The Central government has asked all public sector undertakings to dissuade their employees from taking part in the Bharat Bandh. Employees who go on strike, or even protest, have been threatened with consequences like deduction of wages and disciplinary action.
( With inputs from IANS )