Japanese big manufacturers' business confidence worsened in June from three months ago, the Bank of Japan's closely watched quarterly "tankan" survey showed on Monday.

The headline index for big manufacturers' sentiment stood at plus 21 in June, versus plus 24 three months ago and down for a second straight quarter, the tankan showed.

It was the first time since the final three months of 2012 that big manufacturers' mood soured for two quarters in a row.

The headline index compared with the median estimate of plus 22 in a Reuters poll of analysts, and is expected to stay flat over the next three months, it showed.

The survey also showed big firms plan to raise their capital spending by 13.6 percent in the financial year from April 2018, versus economists' median estimate of a 9.3 percent gain.

The tankan's sentiment indexes are derived by subtracting the number of respondents who say conditions are poor from those who say they are good.

A positive reading means optimists outnumber pessimists.