Arrests made and details revealed about the Aug. 17 Bangkok bombing that killed 20 people have raised the question of whether members of an ethnic and religious minority from China's far west were involved. A primer on the Uighurs, the repression they face in China and their presence abroad:

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WHO ARE THE UIGHURS?

The Uighurs (pronounced WEE-gurs) are a Turkic-speaking Muslim ethnic group native to China's far western region of Xinjiang, which was sporadically controlled by Chinese dynasties over the centuries. They have long complained of ethnic discrimination and religious restriction under the Chinese government, which is dominated by members of the Han ethnic group. Several decades of economic development have brought an influx of Han people into the Uighurs' oil-rich home region. Uighurs have felt marginalized in the region's economic boom, sparking ethnic tensions that erupted in the late 1990s and then again about a decade later, culminating in rioting that left nearly 200 dead in the regional capital of Urumqi in 2009.

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RECENT UNREST

Since 2009, there have been frequent attacks on police stations, military checkpoints and government buildings in Xinjiang. The violence has spilled into other regions with Uighur militants accused of mounting attacks in train stations, markets and even a public square in Beijing. In March 2014, a group of Uighurs — including two women — slashed indiscriminately at crowds at a train station in the southwestern city of Kunming, killing 31. In May of 2014, a bomb assault on a market in Urumqi left 43 people dead.

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BEIJING'S RESPONSE

Beijing has long been wary of independence-minded militants in Xinjiang and has kept tight controls over the region. Beijing began labeling the militants terrorists in 2001 in a bid to win international support for the struggle against the militants. Scholars have argued that China's stifling policies in the region — including restrictions on beards and veils — have marginalized the Uighurs and fueled militancy. Last year, well-known Uighur economist Ilham Tohti, who had urged Beijing to review its policies in Xinjiang to foster reconciliation, was convicted of inciting separatism and sentenced to life in prison. In response to the 2014 attacks, Beijing launched a one-year crackdown on terror cells in Xinjiang, executing and jailing hundreds of people on terrorism-related charges.

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FLEEING CHINA

Uighurs have been fleeing China in recent years, often by way of Southeast Asia. Rights advocates say they are escaping repressive rule, but Beijing says many are leaving to join jihad with the intention of returning to China to carry out terrorist attacks. Courts in Xinjiang cities of Hotan, Kashgar and Karamay recently jailed Chinese smugglers who helped Uighurs cross illegally into Vietnam, as well as several Uighurs who unsuccessfully tried to emigrate illegally. While there are large Uighur diasporas in Europe and the United States, Turkey is the destination of choice for most seeking to leave China. Turkey's government is under intense public pressure to support the Uighurs, leading to tensions in Ankara's relationship with Beijing.

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THAILAND'S REPATRIATION

In late 2014, the Thai government detained hundreds of migrants believed to be Uighurs in refugee camps, including women and children. Many refused to speak to Chinese officials, claiming to be Turkish, and many obtained legitimate Turkish passports and later settled in Turkey. However, on July 9 of this year, Thailand repatriated more than 100 of the Uighurs — mostly men — who were wanted by China as terror suspects. This drew criticism from Uighur advocates, human rights groups, the U.S., the United Nations and others, all concerned that the returnees would be persecuted. Video footage by Chinese state media showed the men hooded and under tight security. Chinese authorities have granted no independent access to any court proceedings for the returnees, allowing the government to control the narrative about them.

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BOMBING CASE

Though there have been many theories about perpetrator and motive, speculation about a Uighur connection to the Bangkok bombing came almost immediately, in part because the bomb went off at a shrine popular with Chinese tourists.

Police have arrested two foreigners, confiscated bomb-making materials from two apartments on the outskirts of Bangkok and are looking for 10 other suspects. The first suspect arrested was found at one of the apartments and possessed a fake Turkish passport. The second, arrested near the Thai-Cambodia border, carried a passport that indicated he was from Xinjiang. Police say they believe the bomber has left the country.

Authorities have intentionally avoided calling the bombing an act of terrorism for fear of hurting Thailand's reputation.