Michiko “fell at her residence, and felt pain, so was scheduled for a check-up at hospital” on Monday, imperial household agency spokesman Katsuyoshi Nakamura told AFP.

Fuji Television and the Asahi daily reported, citing unidentified sources, that the empress emerita would be hospitalised following the check-up at the University of Tokyo Hospital.

It is her first hospitalisation since 2019 when Michiko, who turns 90 on Oct 20, had surgery after being diagnosed with early-stage breast cancer.

Michiko and her husband, former emperor Akihito, are known for modernising the tradition-bound monarchy and bringing it closer to the public.

The first commoner to marry an imperial heir in Japan, Michiko was born in Tokyo in 1934 and attended the exclusive all-girls Christian Sacred Heart School before studying English literature at its university.

She gave birth to Naruhito in 1960 and her second son, Prince Akishino, was born in 1965.

The royal couple were known for their presence at the side of survivors of disasters, especially after the 2011 tsunami that wrecked large parts of eastern Japan.

But right-wing criticism and tabloid scrutiny took a toll on Michiko’s health.

She suffered bouts of stress-related illness, which were sometimes severe, including being treated for intestinal bleeding, and once losing her voice for months.

In 2019, Akihito became Japan’s first monarch to abdicate in two centuries, at the age of 85.