(CNN) -- A gang wielding knives and axes attacked civilians, a police station, government offices and smashed vehicles in a restive region of China, the country's state-run Xinhua news agency reported Tuesday, citing local police.
The incident -- called an "organized and premeditated" terror attack -- occurred Monday in northwestern China's Xinjiang Uyghur Autonomous Region.
Police officers at the scene shot dead dozens of people in the mob. Thirty-one cars were vandalized, including six that were set ablaze.
It was not immediately known how many people were killed and injured.
The location, Shache County, is where nine people authorities describe as terrorists attacked a police station, hurled explosives and torched police cars in December. Police shot and killed eight people in that attack.
There have been other attacks in the region in recent months.
Twenty-nine people were killed and 130 injured when men armed with long knives stormed a train station in Kunming in March. The next month, an attack on a train station in Urumqi, Xinjiang's capital, left three dead, including the attackers, and an attack on an Urumqi market in May killed at least 39 people.
There have been longstanding tensions between Uyghur Muslims, a Turkic people, and Chinese Han people in Xinjiang.
Some Uyghurs have expressed resentment toward China's Han majority in recent years over what they say is harsh treatment from Chinese security forces and Han people taking the lion's share of economic opportunities in Xinjiang.
Amnesty International said Uyghurs face widespread discrimination, including in employment, housing and educational opportunities, as well as curtailed religious freedom and political marginalization.