Inner Mongolia's governor, Yang Jing, said this week that the last 60 years had been ones of "ethnic unity and prosperity".

"For the Mongols, it is 60 years of human tragedy, environmental destruction, social crisis and psychological trauma," said Enghebatu Togochog, president of the New York-based Southern Mongolian Human Rights Information Centre.

"The Chinese came in and got everything while the Mongols lost everything including their basic human rights, fundamental freedom, culture, tradition, lifestyle, and the natural habitat where they maintained their distinct way of life for thousands of years," he said in an emailed statement to Reuters.

"This celebration is not only a justification of China's colonial occupation in Southern Mongolia but also (shows) the determination of China's continuing suppression against the Mongols," Togochog said.

Decades of migration by the dominant Han have made Chinese Mongolians a minority in their own land, officially comprising less than 20 percent of the almost 24 million population of the Inner Mongolian Autonomous Region.

The government says it protects and promotes the rights and culture of the Mongolians.

But Beijing, sensitive about ethnic unrest in strategic border areas like Inner Mongolia and Tibet, keeps a tight rein on minorities.