Hours after the Bank of Japan caught central bank watchers off guard by boosting stimulus, officials were fending off complaints about its communications.

A meeting on Oct. 31 with about 50 analysts and economists on the BOJ's new outlook ran on for two hours — twice the usual time — as the discussion turned to how well Gov. Haruhiko Kuroda and other officials telegraphed their views before the decision, said people who were present.

The questions came like a torrent, with some complaining about the BOJ's bond purchase plan and its communications with the market, according to analysts who asked not to be named as the gathering was private.