TOKYO, June 28 (Reuters) - Japan's government appointed financial regulation expert Atsushi Mimura on Friday as its top currency diplomat, replacing Masato Kanda who battled sharp yen declines this year with the biggest currency intervention on record.

The appointment, made as part of the Ministry of Finance's personnel reshuffle, comes as markets remain on high alert for signs of yen-buying intervention by Tokyo with the currency at 38-year lows below 161 to the dollar.

Currently head of the ministry's international bureau, the 57-year-old Mimura will become vice finance minister for international affairs - a post that oversees Japan's currency policy and coordinates economic policy with other countries.

(Reporting by Makiko Yamazaki; Editing by Muralikumar Anantharaman and Sam Holmes)