TOKYO (Reuters) -Japanese Prime Minister Fumio Kishida's son will resign as his secretary, the premier said on Monday, citing "inappropriate" behaviour after photos of the son and other relatives apparently taken in jest sparked an uproar.

Kishida told reporters that Shotaro Kishida would step down as his secretary from Thursday, saying the change was due to "inappropriate" behaviour at the official residence.

A magazine last week published photos of the younger Kishida and relatives apparently pretending to hold a news conference at the official residence, including the podium where the prime minister usually stands.

Their actions were widely criticised by the opposition. The revelations come at an inopportune time for Kishida, who had gained a boost in popularity with the recent Group of Seven (G7) summit in Hiroshima.

(Reporting by Satoshi Sugiyama; Editing by David Dolan)