Exiled Uighur leader Rebiya Kadeer said Monday her people face a fight for their very existence against Chinese repression as a conference in Japan threatened to drive a wedge between Tokyo and Beijing.

And in a move that looked likely to provoke China, Kadeer also visited Japan's controversial Yasukuni shrine, which commemorates those responsible for the brutal 20th-century invasions and occupations in the name of the emperor.

Ethnic Uighurs and their supporters from around the world gathered in the Japanese capital for a meeting aimed at pressing their claim for freedom from what Kadeer called China's intensifying crackdown.

"Before, we were fighting for our rights, we were protesting against China's oppression," Kadeer told reporters after opening the conference. "But now we face a fight for our existence."

"The situation is now worse than it was in 2009," when Uighurs demonstrated and clashed with the Chinese authorities, she said.

Many Uighurs complain that they are the victims of state-sanctioned persecution and marginalisation in their homeland in northwest China, aided by the migration of millions of Han Chinese into the territory.

The resulting ethnic tensions have led to sporadic flashes of violence in the Xinjiang region, which is home to nine million Uighurs.

Kadeer told the meeting that Beijing's policy of "forcible assimilation" was unacceptable in a modern democracy.

"The Chinese government says it is assimilating and eventually eliminating the Uighur people and other indigenous people... meanwhile China is becoming a global power," she said at the opening of the congress.

"We are peacefully struggling and hope the Chinese government will stop the repressing of Uighur people... and take political reforms to change their authoritarian rule," she said.

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

Xinjiang authorities have also announced measures stipulating all businesses and projects hire more ethnic minority workers, but Uighurs say the rules are not always respected.

After the morning session Uighur representatives, including Kadeer, visited Yasukuni.

The shrine is a hotspot in Japan's relations with its Asian neighbours because it is dedicated to 2.5 million Japanese killed in wars -- including top World War II criminals -- and is often seen as a symbol of the country's wartime aggression.

The visit highlights the strange bedfellows that issues such as Uighur separatism can often create: Japanese nationalists and wartime apologists are apt to make common cause with those who are a thorn in Beijing's side.

"As Uighurs always visit places that are dedicated to people who died for their country, we organised a tour to the shrine," said Tomoyuki Hirose, a member of the Japan Uighur Association.

In Beijing, foreign ministry spokesman Hong Lei said the WUC was "closely related to terrorist organisations".

"We urge the Japanese side to concretely respect China's solemn demands, adopt measures to undo the damage and take concrete measures to uphold the larger interest of China-Japan relations," he said.

The gathering came after Japanese Prime Minister Yoshihiko Noda met his Chinese opposite number Wen Jiabao and South Korean President Lee Myung-Bak in a summit focusing on economic ties and the region's response to North Korea.

Noda and Wen met Sunday for one-on-one talks, but reports from Beijing Monday suggested the Chinese had sought to avoid a second high-level meeting as a way of expressing displeasure over Japan allowing the conference to go ahead on its soil.

This year's conference is the fourth after previous editions were held in Munich and in Washington.

Kadeer said participants from more than 20 countries were at the meeting, which she said was being held in "the most democratic country in Asia".

"I am grateful for the Japanese government for issuing visas for us," she said.

"We had hoped 200 or 300 Uighurs could have gathered here, but some of our delegates were not allowed to get visas because of Chinese pressure on their countries of residence," she told reporters.