Japanese big manufacturers expect conditions to worsen significantly in the next three months, responses to a Bank of Japan survey collected after the March 11 earthquake showed on Monday. It was a reversal of the full survey results.

The BOJ separated figures in its tankan survey of corporate sentiment for March into responses obtained before and after the earthquake to obtain a clearer picture of how firms perceived the effects of the devastation.

The post-quake index for big manufacturers' sentiment was plus 6 for March, unchanged from the full survey.

But the index for June was seen at minus 2 against the full survey's plus 2, indicating that big manufacturers expect to turn pessimistic.

The separated survey figures are the first such data to quantify the impact of the quake, tsunami and a subsequent nuclear crisis on business confidence. But the BOJ warns against reading too much into the tankan because its post-quake sentiment index only takes into account the views of 23.6 percent of the respondents to the survey.

In the regular tankan survey for March was compiled from February 24 to March 31.

(Reporting by Rie Ishiguro and Tetsushi Kajimoto)