China has vowed to ramp up patrols and "crack down upon terrorist groups" after staging large military exercises in the ethnically-divided Xinjiang region following clashes that killed at least 35 people.

Beijing also dispatched two high-ranking officials to the far western region Saturday following a top level Communist Party meeting presided over by President Xi Jinping.

"We will step up actions to crack down upon terrorist groups and extremist organisations and track the wanted," Yu Zhengsheng, a member of the party's Politburo Standing Committee, said after arriving in the Xinjiang capital Urumqi, the state news agency Xinhua reported late Saturday.

China often labels outbreaks of sporadic unrest in the region as terrorism -- claims denied by rights groups for the mostly Muslim Uighur minority who blame unrest on economic inequality and religious repression.

Meng Jianzhu, another senior party official, was also in Urumqi making "detailed anti-terror arrangements", Xinhua said.

He called for "24 hour patrols (in) all weather conditions" according to a report by the state news agency on Sunday.

Their visit and the exercises suggest Beijing sees maintaining stability as a priority ahead of the fourth anniversary on July 5 of riots in Urumqi between members of Uighur and Han Chinese communities which left around 200 dead.

Xinhua also called for tough measures against those responsible for the recent "terror attacks" in a commentary on Sunday.

Saturday's exercises saw large sections of the city shut down as military vehicles took to the streets with at least 1,000 personnel from the People's Armed Police, part of China's armed forces responsible for law enforcement and internal security during peacetime.

The state run Global Times newspaper Sunday described the exercises as "ceremonies... to support the fight against terrorism".

"Every year come July 5, there are more patrols, and the armed police force is strengthened, but not of this scale," Wang Tingxiang, a Han Chinese resident of Urumqi told AFP during the exercise.

"All the ethnic groups here get along. It's all good here. Most of the ethnic clashes have probably got something to do with the outside world," he added, repeating a commonly-used official line from Beijing that separatists from outside of China were partly responsible for unrest.

On Sunday exiled Uighur leader Rebiya Kadeer led a protest against the violence in Xinjiang outside the Chinese embassy in Tokyo.

Kadeer, the US-based head of the World Uyghur Congress who is currently visiting Japan, rested a white flower wreath on the embassy's post box. She was joined by around 30 of her supporters.

"The situation there has been very severe. We have repeatedly called for dialogue with the Chinese government," she said in a YouTube message recorded on Friday.

"We have called on China to change the policy and protect Uighur people's human rights, but the government has no intention to listen to us," she said.

China's state-run media on Saturday blamed more than 100 people it branded "terrorists" for sparking "riots" in Xinjiang the previous day.

The unrest occurred in the prefecture of Hotan, where a group "(attacked) a number of people with weapons after gathering at local religious venues", the media said.

It followed clashes on Wednesday which left 35 dead, the worst to hit the western desert region -- home to around 10 million members of the Uighur minority -- since the 2009 riots.

"This is an overt provocation to the security of people's lives and the country's unity, which should be severely cracked down on with decisive measures since terrorism is the enemy of mankind," the Xinhua commentary said Sunday.

"The atrocity was not a consequence of ethnic disputes or religious disagreements in Xinjiang," it added, claiming that the unrest was due to an "intention to disrupt social stability and sabotage interests of the whole Chinese nation".

Xinhua also reported Sunday that police had detained the "only rioter at large" following last Wednesday's violence. Previous reports said 11 men were killed, while another four were arrested at the scene.

Hotan has reportedly been under a curfew since Friday night, and searches for the town on Sina Weibo, China's version of Twitter, were blocked on Sunday. China's army of Internet censors often block searches for sensitive information on the country's hugely popular microblogging sites.

A woman from Hotan told AFP Sunday that her Internet had been cut since the riots, but her mobile phone connection was recently restored.

"I don't know the entire situation but my life is normal here," she added.

Meanwhile, the website of the Xinjiang Daily newspaper -- the official mouthpiece of the local government -- reported on Sunday that 19 people had been arrested for spreading online "rumours".

China closely restricts information about unrest in Xinjiang, and blocked access across the region for several months after the violence in 2009.

In recent decades millions of Han have relocated to Xinjiang -- which is rich in coal and gas -- to find work, in a settlement drive that has caused friction in the community.

Beijing denies repressing ethnic minorities, who make up less than 10 percent of the national population and enjoy some preferential policies.