BEIJING At least 140 people have been killed and hundreds arrested in rioting in the capital of China's northwestern region of Xinjiang.
The following are facts about some major incidents of unrest since 1989 when troops crushed student-led pro-democracy protests centered on Tiananmen Square in Beijing.
MARCH - Beijing said at least 16 people were killed and more than 100 injured during three days of pro-independence riots in Tibet's regional capital Lhasa. Exiled Tibetans said as many as 60 people died.
JUNE 4 - People's Liberation Army troops and tanks crushed the Tiananmen protests on June 3-4. The Beijing city government at the time put the death toll at more than 200 while insisting no one died on the square itself. But independent groups have estimated that hundreds, perhaps thousands, died.
SEPTEMBER - A cartoon about Muslims and pigs in a Chinese joke book sparked mass protests in the northwestern provinces of Gansu and Qinghai. Thousands of paramilitary police stormed a mosque taken over by armed Hui Muslims in Xining, provincial capital of Qinghai, and opened fire, wounding more than 10.
FEBRUARY 5 to 10 - About 1,000 people, mostly Uighur farmers and unemployed youths, rampaged through Yining near the border with Kazakhstan. China said nine people were killed and at least 198 wounded. Uighurs in exile said that the real death toll was between 80 and 90.
FEBRUARY 25 - A series of bombs placed on buses in Urumqi killed four people and wounded more than 60.
NOVEMBER - At least seven people were killed and 42 hurt in the central province of Henan in rioting sparked by a car accident involving an ethnic Han Chinese and a member of the Hui Muslim minority.
DECEMBER - Paramilitary police opened fire on residents of Dongzhou village in southern Guangdong province. They were protesting about lack of compensation for land taken for a power plant. China said three villagers were killed, though some villagers and reports put the toll higher.
MARCH - Protests and riots spread from Lhasa to other Tibetan areas. China said 19 were killed by rioting in Lhasa while exile groups say about 200 Tibetans died in the crackdown.
AUGUST 4 - Seventeen armed police were killed in a bomb and knife attack in the far western city of Kashgar in Xinjiang. Six days later, suspected Muslim separatists and suicide bombers launched a dozen attacks in Kuqa, southern Xinjiang, killing 11 people in the blasts and a subsequent shootout with police.
In recent years, China has seen an increasing number of scattered mass incidents, sometimes involving thousands of people, sparked by resentment over issues like corruption, pollution, land seizures and biased handling of court cases.
(Reporting by Yu Le, Liu Zhen and Benjamin Kang Lim; Editing by Emma Graham-Harrison)