More than 100 people, riding motorbikes and wielding knives, have attacked a police station in China's ethnically divided western region of Xinjiang.

The attack in the remote desert city of Hotan, a heavily ethnic Uighur area, comes two days after the region's deadliest unrest in four years that resulted in the deaths of 35 people.

China called the incident a "terrorist attack".

Xinjiang is home to the mainly Muslim Uighur people who speak a Turkic language.

There has been tension in the past due to what they say are Chinese government restrictions on their culture, language and religion.

China says it grants Uighurs wide-ranging freedoms and accuses extremists of separatism.

President Xi Jinping, who took office in March, has called for the unity of all ethnic groups in China.

In the latest incident, the Global Times - owned by Chinese Communist Party mouthpiece, the People's Daily - said "troublemakers" gathered at religious venues before riding on motorcycles to attack a police station in the city's Moyu county.

Authorities are counting the number of casualties and searching for suspects, the Global Times said.

In a separate incident, some 200 people attempted to "incite trouble" at a major shopping area in Hotan, the newspaper said. It said police defused the situation.

Yu Zhengsheng, a member of the Politburo Standing Committee, the party's inner circle, pledged to step up "action to crack down upon terrorist groups and extremist organisations" at a meeting with government officials in the regional capital Urumqi, state news agency Xinhua said.

Chinese authorities have increased security in Urumqi, the Global Times said.

Photographs on Chinese microblogs showed dozens of military trucks with riot police patrolling the streets.

The increased security comes almost a week before the fourth anniversary of the July 2009 riots in Xinjiang that pitted Uighurs against ethnic Chinese, resulting in nearly 200 people being killed.