Exiled Uighur leader Rebiya Kadeer claimed Thursday the Chinese government used military force in the latest episode of what she calls "ethnic cleansing" in the troubled region of Xinjiang.

Her remarks came after Chinese state media said a court in the region jailed nine people for promoting racial hatred and "illegal religious activity" online.

Twenty-one people, including police officers, were killed in violent clashes in the ethnically divided region on April 23, officials have said.

Chinese state media has made no mention of any military involvement in the incident, with an earlier report saying gunfights had broken out after police tried to search the home of locals suspected of possessing illegal knives.

Beijing says six "terrorists" and 15 police and other workers were killed -- among them 10 from China's mostly Muslim Uighur ethnic minority.

But Kadeer told journalists in Tokyo the military had been called in and had carried out killings.

"Security officers searched local people's houses, and police called the army," she said.

"Police and the army cooperated in killing people in that area," she said, adding the military had used explosives.

"We watched some videos of the area where the incident happened, and we cannot see any person living in that area. Just burning and collapsing ...houses," she said, speaking through an English translator.

She said China's state media was calling Uighurs "terrorists" because they had knives, which she said they used for cutting vegetables.

Kadeer, who is in Japan on a week-long lecture tour, did not provide reporters with any evidence of her claims.

Her comments came as courts in the Aksu and Kashgar regions of Xinjiang, both of which have majority Uighur populations, sentenced nine people to between two and six years in prison, for promoting "ethnic hatred" and other crimes, the state-run Legal Daily said on Thursday.

One jailed for six years had downloaded material which preached "holy war", the report said adding that the other eight men smashed electrical equipment under the influence of "illegal religion...and religious extremism".

It added that regional authorities had detained two other people for promoting "religious extremism" online.

Xinjiang is home to around nine million Uighurs, many of whom complain of religious and cultural repression by Chinese authorities -- accusations the government denies. The region is regularly hit by unrest.

Officials and state media blame the unrest on "terrorists" but some experts say the government has produced little evidence of an organised terrorist threat, adding the violence stems more from long-standing local resentment.

The region has been under strict security since July 2009, when bloody ethnic riots broke out in the capital Urumqi.

Beijing says it has poured money into Xinjiang in a bid to raise living standards and boost the local economy.

Kadeer claimed "special" police in Xinjiang have the right to raid Uighur homes and "they can kill easily, without permission" from the government.

"We cannot talk about our culture, education and language. We talk now to the international world how to save our lives in our society," she said.

"I hope all the international world will not be patient with this ethnic cleansing policy," she said.

Kadeer, the US-based head of the World Uyghur Congress, visited Japan in May last year, in a tour that led to Chinese criticism of Tokyo.