BEIJING  — More than a hundred people riding motorbikes and wielding knifes attacked a police station in China's ethnically divided western region of Xinjiang, state media said on Saturday, in the latest unrest to hit the region in the past week.

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. Many of them chafe at what they call Chinese government restrictions on their culture, language and religion. China says it grants Uighurs wide-ranging freedoms and accuses extremists of separatism.

The animosity between the majority Han Chinese and the Uighurs poses a major challenge for China's Communist Party leaders. 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 organizations" 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.

In a sign of the gravity of the situation, Xinjiang's top party chief Zhang Chunxian said: "We should be clearly aware of the complex and acute nature of the long-term struggle against separatism," according to the Xinjiang Daily, the official newspaper of the region.

"For those who dare to defy the law, the criminals who engage in violent terrorist activities have to be punished. We can't tolerate them, we have to hold no punches," the People's Daily said in a front-page editorial.