Bank of Japan policymakers Thursday rejected a proposal by a deputy governor to expand its asset-buying program by ¥5 trillion to cope with last month's historic disaster.

The other eight members of the Policy Board voted against Deputy Gov. Kiyohiko Nishimura's proposal to increase a ¥40 trillion program to inject cash into the market, according to a statement issued after the BOJ Policy Board meeting. The policymakers decided unanimously to keep the benchmark overnight rate between zero and 0.1 percent.

Nishimura's proposal underscores the pressure the central bank is facing to provide further monetary stimulus as the extent of damage from last month's disaster becomes clear. Government data this week showed a record decline in industrial production in March and retail sales slumping most in 13 years.