Prince Hisahito, who is second in line to the imperial throne, has tested positive for COVID-19, the Imperial Household Agency said Thursday.

The nephew of Emperor Naruhito has a high fever and will rest at his residence until Monday, it said, adding the prince's parents, Crown Prince Akishino and Crown Princess Kiko, have tested negative.

The prince, a second-year student at the high school at Otsuka, University of Tsukuba, had a fever on Wednesday after returning from school but tested negative for COVID-19 at the time.

With the fever unabated on Thursday morning, he retook the test, and the infection was confirmed, the agency said.

The crown princess and crown prince's news conference at the Akasaka Estate in Tokyo about their official visit to Vietnam scheduled for later this month has been postponed.