Filed at 9:16 p.m. ET
URUMQI, China (AP) -- Chinese leaders bowed to public demands and sacked the head of a western city wracked by communal violence and a bizarre string of needle attacks, hoping to calm uneasy mobs and end protests that percolated for a third day Saturday.
The removal of Urumqi's Communist Party Secretary Li Zhi came amid reports of police again dispersing crowds outside Urumqi's government offices using tear gas, and more unconfirmed reports of needle attacks, including one on an 11-year-old boy in a downtown square.
The city's chief prosecutor announced further details about four people arrested over the attacks, but offered little to back up the government's claims that they were an organized campaign to spread terror.
Protesters marched by the thousands Thursday and Friday demanding the resignation of Li and his boss, Xinjiang party secretary Wang Lequan, for failing to provide adequate public safety in the city. Also sacked was the police chief of Xinjiang, China's westernmost region that abuts Central Asia and whose capital is Urumqi.
An Urumqi government spokeswoman and the official Xinhua News Agency gave no reasons in announcing the changes. But July's riot was the worst communal violence in more than a decade in Xinjiang -- where Uighur separatists have waged a sporadically violent campaign for a homeland. The renewed protests this week underscored the difficulties authorities were having in reasserting control.
The firing may also help quash calls to dismiss Wang -- a member of the country's ruling Politburo and an ally of President Hu Jintao.
''I would say that this is the sacrificial lamb,'' Russell Leigh Moses, an analyst of Chinese politics based in Beijing. ''But it will be interesting to see what the reaction in the streets is and whether this satisfies people's anger or not.''
Li, a 58-year-old career official in Xinjiang, played a visible role during the July violence and recent protests. In July he climbed atop a car with a megaphone and urged an angry crowd of Han Chinese to show their patriotism by fighting separatists but not ordinary Uighurs.
On Thursday, when more than 10,000 people protested through the city, Li and Wang separately waded into crowds to meet with protesters to defuse tensions, only to be greeted with shouts to ''step down.''
''Do I not know that I should protect my brothers and sisters?'' Li told them, according to footage aired on Urumqi's TV station and recounted by a local newspaper editor.
It wasn't clear whether protesters would be assuaged and two key demands -- an end to the syringe attacks and the swift punishment of those responsible for the July rioting -- have yet to be met.
Urumqi's prosecutor said among the 21 suspects in custody, all of them Uighurs, two jabbed a taxi driver with a heroin-filled syringe to steal 710 yuan ($105) to buy drugs.
Overall, a show of force by thousands of troops on patrols restored calm to much of the city. Paramilitary police manned checkpoints around government and party offices and put up barricades backed by tanks at entrances to a heavily Uighur neighborhood -- a sign that officials were worried the mainly Han protesters might try to storm in.
More than 500 people have sought treatment for stabbings, though only about 100 showed signs of having been pricked, according to state media reports. Members of a visiting People's Liberation Army medical team said they conducted checks on 22 patients who showed clear signs of having been stabbed and found no indication that radioactive or biochemical substances had been used in any of the attacks.
Tests were still being conducted for HIV, hepatitis, and sexually transmitted diseases, and the results would be made public at a time to be determined by the Xinjiang government, said Qian Jun, one of the team's leaders.
Urumqi Prosecutor Udgar Abdulrahman said four of the detained suspects -- three men aged 19, 34 and 47, and one woman, 22 -- were charged with endangering public security. Aside from the two who stabbed the taxi driver for drug money, Abdulrahman said the others acted separately. One jabbed a fruit seller and the other a police officer. No motive was given for the other attacks.
Abdulrahman did not cite an obvious political link to the stabbings, but said he believed there was a degree of coordination. ''At this point, we think there is a plot and it is organized,'' he said.
Public Security Minister Meng Jianzhu said Friday the same Muslim separatists that Beijing blames for the July 5 ethnic rioting also orchestrated the syringe attacks.
The government has not provided an ethnic breakdown of the five killed in Thursday's protests. A report in Urumqi's Morning Post on Saturday said a ''small number of people became overexcited and lost control of themselves'' during the demonstrations. It said casualties included police, paramilitary troops and innocent civilians, but gave no specifics.
By most accounts, the July 5 riot started after police confronted peaceful Uighur protesters, who then attacked Han Chinese. Days later, Han vigilantes tore through Uighur neighborhoods to retaliate.