The business confidence of major companies improved slightly in March from three months earlier, the Bank of Japan said Friday, while forecasting an almost certain deterioration in sentiment as a result of the economic impact of the Tohoku disaster.

The diffusion index in the central bank's "tankan" survey showed the sentiment of big manufacturers improved to plus 6 from December's plus 5, logging the first increase in two quarters. Economists surveyed had forecast a fall to plus 4.

As for major nonmanufacturers, the index rose from plus 1 to plus 3, also the first gain in two quarters and better than the average projection of a decline to zero.