A prominent political activist for China's Uighur ethnic minority, Rebiya Kadeer, will be allowed into Japan during this week's Group of 20 leaders' summit, her supporters have said.

Japanese government sources have confirmed Tokyo issued a visa to Kadeer, despite calls not to do so from Beijing. She plans to protest human rights violations by the Chinese government during her stay, which will coincide with President Xi Jinping's visit to Osaka for the summit.

Roughly 10 million Uighurs live in China, mainly in the far-western Xinjiang autonomous region. The Chinese government has been criticized for its oppressive treatment of the majority-Muslim group, including by sending large numbers to mass detention camps for what is described as re-education.

Former president of the World Uyghur Congress and current president of the Free Indo-Pacific Alliance, a group that represents exiled minorities including Tibetans, Kadeer herself fled China after being labeled a separatist, and now lives in the United States.

The visa application was submitted on June 7 and the visa issued Wednesday, on the grounds that Kadeer had already traveled to Japan more than 10 times and that there was no legal reason to keep her from doing so again, the government sources said.

Kadeer's supporters said Friday that the process took longer than for previous visas, which only took a week or so to be issued.

According to the government sources, Beijing asked Tokyo in December to handle the matter "appropriately." The request was made directly to the office of Prime Minister Shinzo Abe via a senior official from China's Ministry of State Security, they said.