TOKYO, Sept 21 (Reuters) - The 30-year Japanese government bond yield rose to an 11-month high on Friday after the Bank of Japan trimmed its purchase of super-long debt at a regular buying operation.

The central bank on Friday offered to buy 50 billion yen ($444 million) of 25- to 40-year JGBs, down from 60 billion at its previous operation on Tuesday.

The BOJ often tweaks the amount of bonds it purchases at operations as part of its yield curve control scheme.

The 30-year yield was 2.5 basis points higher at 0.875 percent, the highest since October 2017.

The 40-year yield also rose 2.5 basis points, to 1.015 percent, the highest since January. ($1 = 112.5200 yen) (Reporting by the Tokyo markets team; Editing by Sunil Nair)