The crowd of Muslim Uighurs started out as a peaceful protest of 300, demanding an investigation into a fight between Uighurs and Han Chinese workers at a factory in Southern China last month, which left two people dead.

However, it quickly grew to between 1,000 and 3,000. When the protesters refused to disperse, police moved in and started pinning them to the ground, hauling away at least 40 protestors.

Police entered Urumqi, a largely Uighur-populated area, and used batons, sling-shots and bamboo poles. The Internet was cut off or slowed down, and mobile phone services were interrupted.

State television showed the Uighur protesters attacking native Han Chinese in the streets.

Violence continued into the night and into Monday, when police started to get the situation under control as they shut down traffic in parts of the city.

The Chinese mass media, as well as the Xinjiang government, has placed the blame for the violence on the World Uighur Congress, headed by Rebiya Kadeer, a former businesswoman who was arrested in 1999 on charges of undermining Chinese national security and released on bail in 2005. She now lives in the United States.

Burnt wreckage of a bus in a street in Urumqi in China's far west Xinjiang province on July 6, 2009 (AFP Photo / Peter Parks)

"We also must expose Rebiya and those like her … we must tear away Rebiya's mask and let the world see her true nature," Xinjiang's top Communist Party official, Wang Lequan said.

However, the Uighur community saw it very differently.

"We are extremely saddened by the heavy-handed use of force by the Chinese security forces against the peaceful demonstrators," said Alim Seytoff, vice president of the Washington, D.C-based Uyghur American Association.

"We ask the international community to condemn China's killing of innocent Uighurs. This is a very dark day in the history of the Uighur people," he said.

Tensions have always been high between the Uighurs and Chinese, where some Uighurs groups have been pushing a separatist campaign.

In 1955, the creation of the Xinjian-Uighur autonomous region of the People’s Republic of China was made official.

However, the region has since seen decades of unease due to the migration of ethnic Chinese to the region, with the sense of the rights infringement of non-Chinese causing deep dissatisfaction with their situation.

While in China, and particularly in Xinjiang, Uighurs make up the largest ethnic group, in Urumqi they have become a minority, as large numbers of Han Chinese migrants have flooded to the city of 2.3 million.

This has been a constant source of trouble for the native Uighur population.

The Chinese authorities have experienced a great deal of separatist activity in the region, particularly from one group, the East Turkestan group, whom China considers a terrorist organization supported by other foreign terrorist organizations including al-Qaeda.