A Japanese kindergarten that has ties to Prime Minister Shinzo Abe's wife, Akie, has apologized over online comments that domestic media described as possible hate speech against Koreans and Chinese people.

The private Tsukamoto kindergarten in Osaka, western Japan, has been visited by Akie Abe and is operated by Moritomo Gakuen, an educational institution that plans to open an elementary school in April with the prime minister's wife as honorary principal.

Kyodo news agency reported on Friday that the kindergarten had apologized after referring to "irresponsible" South Korean and Chinese parents on its home page.

"We apologize for expressions about foreigners that caused misunderstanding," the kindergarten said on its web site.

The school, however, denounced "unjust, slanderous and defamatory Internet-based articles about this kindergarten" and it said it would keep fighting against "malicious criticism".

Criticism of Korean residents and Chinese people is a common feature of right-wing rhetoric in Japan, where ethnic homogeneity has been a source of pride for many conservatives.

Separately, the Osaka prefectural government is considering whether to take action over derogatory expressions about Koreans living in Japan and Chinese used by the kindergarten in a document sent to students' parents last year, an Osaka official said.

The Tsukamoto kindergarten aims to instill in its 3- to 5-year-old students a sense of patriotism with a curriculum focused on Japanese traditions and culture.

Abe was grilled in parliament last week about possible ties to Moritomo Gakuen, including whether he knew his name had been used to solicit donations for the elementary school.

Abe said then he had rejected a request to have the school bear his name because it was not appropriate for an incumbent lawmaker and was unaware his name had been used in seeking donations.

An official at the prime minister's office declined comment on any specific remarks by the school because they had not seen them.

But the official, who declined to be identified because of the sensitivity of the subject, added: "When it comes to the issue of discrimination based on nationality, ethnicity or race, it cannot be tolerated and it is extremely important to have consideration for others and to have mutual understanding."

Yasunori Kagoike, the principal of the kindergarten and president of Moritomo Gakuen, heads the Osaka branch of Nippon Kaigi, or Japan Conference, a nationalist lobby group with close ties to the prime minister and his cabinet.

Kindergarten officials were not available for comment.