Chinese authorities have tightened security in the western region of Xinjiang ahead of the first anniversary of the country's worst ethnic violence in decades.

State media said police have installed 40,000 high-definition surveillance cameras with "riot-proof" shells throughout the regional capital city of Urumqi.

The Xinjiang Economic daily on Friday said the security cameras were installed in several thousand public buses, at bus stations, along roads, as well as in schools and supermarkets.

Tensions between the region's minority Uighurs and majority Han Chinese turned deadly in Urumqi last July 5.

The government says nearly 200 people were killed and about 1,700 injured in the unrest, with Han making up most of the victims.

China has blamed ethnic separatists and Muslim extremists for stoking unrest in Xinjiang over the past decade.

Xinjiang, a vast, arid but resource-rich region that borders Central Asia, has more than eight million Uighurs, and many are unhappy with what they say has been decades of repressive communist rule by Beijing.

Many also complain about an influx of Han Chinese – China's main ethnic group – that they say leaves them economically and culturally marginalised in their homeland.