Xinjiang, officially Xinjiang Uygur Autonomous Region (XUAR), is an autonomous region of the People's Republic of China (PRC), located in the northwest of the country close to Central Asia. Being the largest province-level division of China and the 8th-largest country subdivision in the world, Xinjiang spans over 1.6 million square kilometres (620,000 sq mi) and has about 25 million inhabitants. Xinjiang borders the countries of Mongolia, Russia, Kazakhstan, Kyrgyzstan, Tajikistan, Afghanistan, Pakistan and India. The rugged Karakoram, Kunlun and Tian Shan mountain ranges occupy much of Xinjiang's borders, as well as its western and southern regions. The Aksai Chin region, administered by China, is claimed by India. Xinjiang also borders the Tibet Autonomous Region and the provinces of Gansu and Qinghai. The most well-known route of the historic Silk Road ran through the territory from the east to its northwestern border. It is home to a number of ethnic groups, including the Turkic Uyghur, Kazakhs and Kyrgyz, the Han, Tibetans, Hui, Tajiks, Mongols, Russians and Xibe. More than a dozen autonomous prefectures and counties for minorities are in Xinjiang. Older English-language reference works often refer to the area as Chinese Turkestan, East Turkestan and East Turkistan. Xinjiang is divided into the Dzungarian Basin in the north and the Tarim Basin in the south by a mountain range. Only about 9.7% of Xinjiang's land area is fit for human habitation. With a documented history of at least 2,500 years, a succession of people and empires have vied for control over all or parts of this territory. The territory came under the rule of the Qing dynasty in the 18th century, later replaced by the Republic of China government. Since 1949 and the Chinese Civil War, it has been part of the People's Republic of China. In 1954, the Xinjiang Bingtuan (XPCC) was set up to strengthen border defense against the Soviet Union and also promote the local economy by settling soldiers into the region. In 1955, Xinjiang was administratively changed from a province into an autonomous region. In recent decades, abundant oil and mineral reserves have been found in Xinjiang and it is currently China's largest natural gas-producing region. From the 1990s to the 2010s, the East Turkestan independence movement, separatist conflict and the influence of radical Islam have resulted in unrest in the region with occasional terrorist attacks and clashes between separatist and government forces.