Chinese leaders removed the Communist Party chief of the restive western city of Urumqi yesterday, trying to appease public anger following violent protests last week that the government worries could re-ignite deadly ethnic rioting.

The government's Xinhua News Agency, in announcing the decision, did not give a reason for the firing of Li Zhi. But protesters who marched in their thousands on Thursday and Friday have demanded Li's and his boss's dismissal for failing to provide adequate public safety in the city.

A series of stabbings with hypodermic needles that the government blames on Muslim separatists touched off the protests, which left five dead and further unnerved the city still uneasy from July rioting that killed 197, mostly members of China's Han majority attacked by Muslim Uighurs.

Trying to get control of the situation, leaders replaced Li with Zhu Hailun, who has been the party's top official in charge of law enforcement in Urumqi. Also sacked was an official in the police department for Xinjiang, China's westernmost region whose capital is Urumqi. The official's name was not released.

Besides assuaging public anger, the Chinese leadership hopes sacking Li will alleviate calls to remove Xinjiang party secretary Wang Lequan, a member of the ruling Politburo and an ally of the president, Hu Jintao.

Both Li and Wang took visible roles in trying to defuse the protests, wading into crowds to meet protesters on Thursday only to be greeted with shouts to "step down".

Yesterday, thousands of troops, backed by tanks and metal barricades, patrolled Xinjiang's regional capital. Paramilitary police manned checkpoints on streets around government and Communist Party headquarters, where security forces fired tear gas on Friday to disperse angry crowds of Han Chinese who say the government isn't doing enough to protect them from extremists among the native Uighur population.

Entrances to the city's Muslim quarter remained blocked by thousands of troops backed by heavy metal barricades and tanks. Traffic was barred from much of the central area in the city of 2.5 million, and many shops were closed.

There were no updated figures for the number of needle attacks, but unconfirmed reports of new incidents continued to spread. Angry Han rushed to the southern edge of the city's central square after people said two Uighur men had attacked an 11-year-old boy. Riot police quickly cleared the area.

The needle attacks began on 20 August, though were not publicly reported until Wednesday following days of rumours. Urumqi deputy mayor Zhang Hong said on Friday that 21 suspects have been detained, with four people indicted. He said all were Uighurs, while most victims were Han.

Local police said hospitals in Urumqi were treating 531 people who believed they were attacked. Of those, 106 showed obvious signs of needle attacks.

Details of the deaths were few, although Zhang said on Friday that all occurred on Thursday, the first day of the street protests, and resulted from "small-scale clashes". He said two of those killed were "innocent", while investigations into the other three deaths were continuing.

A report in Urumqi's Morning Post yesterday said a "small number of people became overexcited and lost control of themselves" during Thursday's demonstrations. It said casualties included police, paramilitary troops and innocent civilians, but gave no breakdown.

The World Uyghur Congress, a German-based exile group, said Han Chinese attacked over 10 Uighurs during the two days of protests and tried to storm the Nanmen mosque on Friday but were stopped by authorities.

Chinese leaders have accused Muslim separatists of being behind both the needle attacks and July rioting, though Beijing has provided scant evidence to back up the claim. By most accounts, the July riot started after police confronted peaceful Uighur protesters, who then attacked Han Chinese. Days later, Han vigilantes tore through Uighur neighbourhoods to retaliate.

Public security minister Meng Jianzhu vowed the government would speed up charging and prosecuting more than 1,200 people detained after the riots.