The order for the patrols by the People's Armed Police was issued by the Communist Party's top law enforcement official, Meng Jianzhu, at an emergency meeting late on Saturday in Urumqi.

The action came just days ahead of the July 5 anniversary of a 2009 riot between Xinjiang's native Uygur people and Han Chinese migrants in the city that left nearly 200 people dead.

Troops must patrol in all weather conditions, "raise their visibility, maintain a deterrent threat and strengthen the public's sense of security", Meng said, according to a notice posted to the Public Security Ministry's website yesterday.

A Lukqun resident said by phone that troops could be seen patrolling the streets over the past few days.

According to a police statement posted on the Xinjiang government's official website yesterday, the attackers belonged to a 17-member extremist Islamic cell formed in January by a man identified by the Chinese pronunciation of his Uygur name, Aihemaitiniyazi Sidike.

The statement said the cell regularly listened to recordings promoting violence and terrorism and since mid-June had been raising funds, buying knives and gasoline, and casing various sites in preparation for an attack. But last Tuesday authorities captured one of the members.

Fearing they would be discovered before they could act, Sidike ordered the gang to assemble before dawn Wednesday and attack, the statement said.

It said their victims included 16 Uygurs, eight Han and two women.

Police wounded and captured four gang members and seized the last suspect yesterday following a search, Xinhua reported yesterday.

Following that incident, more than 100 knife-wielding people mounted motorbikes in an attempt to storm the police station on Friday in Karakax county in southern Xinjiang's Hotan region, where the population is overwhelmingly Uygur.

Elsewhere the same day, an armed mob staged an attack in the township of Hanairike, according to the Xinjiang regional government's news portal. There was no official word on casualties.

State-run newspapers reported yesterday that Xinjiang was calm, and state broadcaster CCTV ran interviews with pro-government Muslim clerics and residents of Urumqi, both Chinese and Uygur, who denounced violence and expressed confidence in the government's ability to maintain security.

Xinhua said in a separate commentary that "terrorist organisations should be aware that the Chinese nation and its people are determined to safeguard the country's territorial integrity and national unity against all enemies. Any attempt to sabotage will eventually fail."

Associated Press, Reuters and additional reporting by Choi Chi-yuk