Five people have been killed in ethnic¹ unrest in China's western city of Urumqi this week, officials say.

中国官员称，本周西部城市乌鲁木齐种族冲突导致五人被杀。

It was unclear how the deaths happened, but thousands of Han Chinese have been protesting over an unexplained spate²（泛滥，洪水） of stabbings with syringes（鸣管，耳鸣管）.

Many of the protesters blame ethnic Uighur Muslims for the stabbings.

Riot police used tear gas to disperse³ angry crowds earlier, and China's top security official has arrived in Urumqi to try to restore（恢复） order.

In July about 200 people - mostly Han Chinese - were killed in ethnic riots in the city, the capital of Xinjiang region.

Beijing blamed exiled Uighur separatist groups for July's violence.

Xinjiang's population is evenly split between Uighurs and Han Chinese - the country's majority ethnic group. But Hans make up three-quarters of Urumqi's population.

'Undermining unity⁴'

Zhang Hong, vice-mayor of Urumqi, confirmed to reporters that there had been casualties in the latest unrest.

"On Thursday, 14 people were injured and sent to hospital and five people were killed in the incidents including two innocent people," he said.

Mr Zhang gave no further explanation of how the people were killed.

Meanwhile, Beijing has sent its top security official, Meng Jianzhu, to Urumqi.

On his arrival he was quoted by state-run news agency Xinhua as saying the syringe（注射器） attacks were a continuation of the July unrest.

He said the attacks were instigated⁵（教唆，煽动） by ethnic separatist forces seeking to undermine ethnic unity and urged local officials "to restore social order as soon as possible".

But analysts⁶ say Mr Meng's visit reflects Beijing's desire to take control of the situation - and suggests the central government no longer trusts local officials.

'All marches banned'

The BBC's Michael Bristow, in Urumqi, says hundreds of police fanned out across the city on Friday, breaking up angry crowds gathering⁷ at road junctions⁸.

Tear gas was fired to disperse（分散，传播） one group of protesters and there were scuffles（混战） at a crossroads as police moved in to arrest several demonstrators.

Xinhua reported that the authorities had banned "all gatherings⁹, marches or protests on roads or other public venues¹⁰".

The crowds demanded more protection amid media reports saying more than 500 people, almost all Han, have sought treatment for stabbings in the past few weeks.

There is also anger over what many perceive as official slowness in punishing suspects charged over July's riots.

Tension between Xinjiang's Uighur and Han communities has been simmering for many years, but July's ethnic unrest was the worst in China for decades.

It began when crowds of Uighurs took the streets to protest about mistreatment - but their rally spiralled（螺旋） out of control and days of violent clashes followed.