Hong Kong (CNN) China has delved back centuries in an attempt to justify its controversial policies in the far-western region of Xinjiang, where experts say up to 2 million Uyghurs and other predominantly Muslim ethnic minorities have been held against their will in vast detention centers.

In a white paper released Sunday, the Chinese State Council Information Office painted Xinjiang as a religiously diverse community where a number of faiths had co-existed for centuries.

The 6,800-word document, released in full by state news agency Xinhua, said that Xinjiang "respects citizens' freedom to believe in, or not to believe in, any religion."

However, it also said Islam was introduced to region by force during a religious war in the 10th century, which ended Buddhism's centuries of dominance.

"The Uyghur conversion to Islam was not a voluntary choice made by the common people, but a result of religious wars and imposition by the ruling class," the report said.