The mayor of a city in Shizuoka Prefecture, central Japan, has filed a complaint with police against the head of a nursery over his alleged cover-ups of suspected child abuse cases involving its workers.

The mayor of Susono City, Murata Harukaze, submitted the complaint on Monday against Sakurai Toshihiko, who heads Sakura Hoikuen -- a private nursery school authorized by the local administration.

South Korea has reopened a complaint with the World Trade Organization over Japan's tightened export controls on three high-tech materials.

Officials of South Korea's Ministry of Trade, Industry and Energy revealed the reopening to NHK on Thursday.