Something terrible has happened in Urumqi. The Chinese state media says 140 people were killed and more than 800 injured in clashes between police and protesters in the capital of Xinjiang province at the weekend. Uighur groups claim the death toll is significantly higher. Beijing says the local authorities suppressed an anti-Han Chinese pogrom. The Uighurs claim the police fired indiscriminately on peaceful protesters. Whichever narrative is closer to the truth, there is little doubt that this constitutes the bloodiest official crackdown in China since Tiananmen Square 20 years ago.

According to some reports, the trigger for these protests was a fight between Uighur migrant workers and Han Chinese in the city of Shaoguan in south-eastern China last month. But Beijing has accused Uighur groups based overseas of orchestrating the attacks as part of a separatist campaign of terror. This is a familiar tune. Ever since the 11 September attacks on the US in 2001, Beijing has sought to present the Muslim Uighurs as allied to al-Qa'ida and other international Islamist terror groups. There is clearly a separatist movement in Xinjiang, as the sporadic attacks on government targets since the early 1990s demonstrates. But China has produced no evidence of a connection between the Uighur independence movement and foreign terror groups. Moreover, Beijing can hardly be considered an innocent party when it comes to the relations with the Uighurs.

It is true that there has been significant economic development in Xinjiang in recent years. The province's large cities have grown wealthier as development money from Beijing has poured in. But within the velvet glove of economic aid from the Communist Party has been the iron fist of cultural suppression.

Four years ago, Human Rights Watch released a comprehensive report detailing how Beijing undermines Uighur culture and restricts religious freedom in the province. It uncovered Communist Party documents that instruct local officials to forbid the celebration of religious holidays and prevent children from taking part in religious activities. It reported that thousands of political dissidents have been jailed, and that process has accelerated since the report was published. The Old City in Kashgar, an exemplar of the traditional Uighar way of life in Xinjiang, is being demolished, and the pace of Han immigration has increased. Uighurs now constitute a minority in Urumqi.

Beijing has used the same techniques in Tibet, where authorities have encouraged the migration of tens of thousands of Han Chinese, curbed Tibetan Buddhist culture and accused the Dalai Lama, without proof, of orchestrating violent rebellion from abroad. Like the Tibetan plateau, Xinjiang has strategic importance for Beijing. The province is China's largest natural gas producing region and is rich in minerals.

Twenty years after the Communist leadership sent in tanks to crush student protests in Tiananmen, we have a graphic reminder that the Chinese government will brook no challenges to its authority. Despite two decades of rapid economic development and an unprecedented opening up to the rest of the world, China has confirmed that it remains a repressive autocracy intolerant of cultural diversity within its borders and prepared to use extreme force against its own people.

Much has changed in China in 20 years. But much, sadly, also remains the same.