China's Xinjiang troubles - in 60 secs
22 May 2014 Last updated at 14:06 BST
Two cars have been crashed into shoppers at a market in China's restive Xinjiang region, killing 31 people, Chinese media reports say.
The attackers also threw explosives during the attack in the regional capital Urumqi, in what China's Ministry of Public Security called a "violent terrorist incident".
Xinjiang, which is home to the Muslim Uighur minority, has seen a spate of attacks in the past year.
Here are some of the reasons for the unrest - in 60 seconds.
Video produced by Michael Hirst