Attackers in China's restive Xinjiang region have crashed two cars into shoppers at a market, killing 31 people, Chinese media reports say. They also threw explosives during the attack in the regional capital Urumqi. More than 90 people were injured, the state-run Xinhua news agency said. The Ministry of Public Security called it a "violent terrorist incident". Xinjiang, which is home to the Muslim Uighur minority, has seen a spate of attacks in the past year.