TOKYO (Kyodo) -- Princess Aiko, the only child of Crown Prince Naruhito and Crown Princess Masako, has been reluctant to attend school since Monday after being "treated harshly" by boys in her grade, an official of the Imperial Household Agency said Friday.

But an official of the school denied that the 8-year-old princess was directly subject to rowdy behavior of the boys, after the unusual announcement by Issei Nomura, the top aide to the crown prince and princess, about the princess' absence citing problems in school.

Princess Aiko, a granddaughter of Emperor Akihito and Empress Michiko and a second grader at Gakushuin Primary School in Tokyo's Shinjuku Ward, has been complaining of strong anxiety and stomachache, Nomura, grand master of the crown prince's household, told a regular news conference.

The princess missed school in late February due chiefly to mild fever, and attended school Tuesday but left early and has since been absent, he said, adding there are no prospects for her to return to school.

The school has found that a group of boys had dealt rowdily with several of their school mates, including Princess Aiko, Nomura said, adding that the palace has asked the school to address the matter.

He also said the palace has obtained consent from the school to publicize the princess's situation.

At a hastily arranged separate press conference, Motomasa Higashisono, a senior director of the Gakushuin School Corporation that runs a range of schools from kindergarten to university, said, however, "As far as we know, there was no violent behavior targeted at Princess Aiko."

The princess "got scared Tuesday when she went by a boy who dashed out of a classroom," Higashisono said, adding, "It must have reminded her of the rowdy behavior of several boys in the past...and made her uneasy."

The disorderly behavior of the boys included throwing bags, running fast down hallways and shouting around July last year, but calmed down by about November after the school allocated more teachers to deal with them, he said.

Originally a school for imperial and noble family members, Gakushuin has been attended by most members of the imperial family, including Emperor Akihito and Crown Prince Naruhito.

Princess Aiko entered Gakushuin Primary School in April 2008 after finishing Gakushuin Kindergarten in March that year.

Prime Minister Yukio Hatoyama said, "As an individual citizen, I hope she recovers and gets well as quickly as possible."