Japan's top government spokesperson says Prime Minister Kishida Fumio has reprimanded his secretary and son Shotaro over reported merrymaking in the leader's official residence.

Chief Cabinet Secretary Matsuno Hirokazu commented at a news conference on Thursday about an online article of the Shukan Bunshun weekly released the previous day.

The article said Kishida Shotaro, who serves as the prime minister's secretary, held a year-end party with his relatives at the living quarters adjacent to the prime minister's office in December.

The younger Kishida and the participants reportedly frolicked and took photos in a room that is used to receive foreign dignitaries.

The report also said they held a mock news conference, and a participant was photographed lying on a staircase in the residence.

Matsuno told reporters that the facility is for the prime minister and his family to live in, but that it also has official functions to receive guests and carry out other duties.

He called the son's actions inappropriate, and pledged to ensure the residence will be properly used.

Matsuno went on to say that the prime minister gave a strict warning to his son following the report.

A reporter asked if the secretary would be dismissed. Matsuno replied that he understands the younger Kishida will continue his duties with an enhanced sense of responsibility.

Asked if the prime minister was with the son when such photos were taken, Matsuno said he heard that the elder Kishida greeted the participants while they were dining at a private living space.