Mumbai, Aug. 11 -- ICICI Bank, which last revised its average minimum account balance requirements in 2015, has raised the threshold for savings accounts in metro and urban areas to Rs.50,000 from Rs.10,000.

In the surprise move, India's second-largest private-sector lender has also hiked the requirement for semi-urban areas to Rs.25,000 from Rs.5,000 and for rural areas to Rs.10,000 from Rs.5,000.

Mint probes what could have led to this step.

Urban customers who open savings bank accounts with ICICI Bank from 1 August will have to maintain a minimum average balance of Rs.50,000.

Certain exemptions apply-the hike will not apply to existing account holders, salary accounts, basic savings deposit accounts, and zero-balance savings accou...