Gross domestic product fell 0.9 percent in January-March, nearly double the 0.5 percent forecast by analysts, translating into an annualised 3.7 percent decline compared with a 2.0 percent forecast, government data showed on May 18.

Despite the negative surprise, economists still expect the Bank of Japan to keep monetary policy steady when it ends a two-day meeting on Friday while declaring readiness to ease further if the quake's impact proves more lasting that thought.

The second straight quarter of contraction puts Japan effectively into recession with analysts projecting the economy will shrink again in April-June as supply bottlenecks triggered by the March catastrophe continue to weigh on output and exports.

Most economists still see growth resuming in the second half of the year as supplies are gradually restored and reconstruction spending is expected to kick in, thought there are still risks to such a scenario, including possible power shortages in the summer.