Security was ramped up in the capital of China's Xinjiang region, state media reported Friday, the fourth anniversary of ethnic clashes which killed around 200 people.
Two incidents last week in the area, where mostly Muslim Uighurs are the largest group but members of China's Han majority dominate the economy, left at least 35 people dead.
"Wearing helmets, officers patrolled the capital holding guns and shields," said a report by the state-run Global Times, describing the "heaviest security measures since 2009" in the regional capital Urumqi.
China commonly steps up patrols for the July 5 anniversary of the inter-ethnic riots but the report added: "Last week's violence in the region has made authorities particularly watchful."
The date also comes in the run-up to the Islamic holy month of Ramadan.
Yu Zhengsheng, a member of the ruling Communist party's top Politburo Standing Committee, said at the weekend that China would "step up actions to crack down upon terrorist groups", while Meng Jianzhu, another senior official, called for "24 hour patrols".
There was "a heavy presence of armed police officers and police vehicles at all major crossroads in Urumqi", the Global Times said.
The newspaper also reported that tourism had been hit in Xinjiang following unrest last Wednesday in Lukqun township, where 35 were reported dead, and what state media described as "riots" two days later in the prefecture of Hotan, more than 1,000 kilometres (600 miles) away.
"The Global Times learned from local restaurants, hotels and tourist agencies that many tourists chose to cancel their tours in the wake of the violence," it said.