The statement on Friday by the World Uighur Congress (WUC) came on the eve of Saturday's 50th anniversary of the Communist Party's rule over Xinjiang, which had previously been an independent nation known as East Turkestan.
It also came just days after China's top law-enforcement official ordered a strengthened campaign to wipe out "terrorism, separatism and religious extremism" in the region.
"The policies of political oppression, cultural assimilation, economic exploitation, ecological destruction, racial discrimination have gradually turned East Turkestan into a time bomb," the WUC said.
"As a result, severe anti-Chinese sentiment is intensified throughout East Turkestan," it said.
The statement also widely diverged from China's interpretation of the historical background of the region and the circumstances surrounding the establishment of Xinjiang.
Critics say China is trying to
culturally assimilate the Uighurs
It said the late Chinese revolutionary Mao Zedong estalished Xinjiang in 1955 after earlier promising the people of East Turkestan self-determination and full independence.
"China's founder Mao Zedong died three decades ago, but China's strategic, political and economic objectives in East Turkestan have remained unchanged," the WUC said.
"The present Chinese leaders are continuing the same policy to transform East Turkestan completely into a Chinese colony, culturally assimilate the Uighur people, and economically exploit their natural resources."
Beijing views Xinjiang as an invaluable asset because of its crucial strategic location near Central Asia and its large oil and gas reserves. Over the last decade a huge influx of Han Chinese have immigrated into the region.