China expressed its "strong dissatisfaction" after exiled Uygur separatist Rebiya Kadeer arrived in Japan Tuesday afternoon for a 10-day visit.

"China expresses its strong dissatisfaction," foreign ministry spokesman Ma Zhaoxu told reporters Tuesday. "We want to reiterate that China is firmly against national separatism and is firm in upholding our national unity."

However, Ma did not directly criticize Japanese Prime Minister Yukio Hatoyama.

"Some forces in Japan plan to facilitate Kadeer's visit to Japan, despite China's grave concerns," he said.

Kadeer last visited Japan in July, but this week's trip will be her first since Hatoyama, who has vowed to deepen ties with Beijing, took office last month.

No official response from Japan has been made yet.

Kyodo News cited a senior Japanese official as saying that Kadeer's visa was issued under Japanese law and there can be no cause for criticism. Another government source said no conditions were placed on the visa, such as refraining from political activities.

Speaking upon her arrival at Narita airport near Tokyo, Kadeer said that she wants Japan to hold talks with China, and "pressure the Chinese government to change its policies on ethnic minority groups."

According to Japanese newspaper Sankei Shimbun, during her stay, Kadeer will attend exchange events at universities in Tokyo, western Japan and the Kyushu area, and participate in an event commemorating publication of a book about her.

"Kadeer's Japan trip may lead China to cool the warm relations begun with Hatoyama's cabinet when he visited Beijing a couple of weeks ago. Let's see how Chinese Premier Wen Jiabao will react when the 12th summit between the ASEAN and China, Japan and South Korea starts Friday," said Su Hao, director at the Asia-Pacific Research Center of China Foreign Affairs University.