URUMQI: Residents in Urumqi city demanded further action Sunday after the sacking of two top officials in the restive Xinjiang region over syringe attacks that sparked deadly protests.

The sceptical reaction to the sackings came as a top regional official said the government would send 600 officials to visit local Han residents in a bid to ease tensions, state media reported.

The Communist Party chief of Xinjiang's capital Urumqi and the region's top police official were dismissed in the wake of the protests that left five people dead, but residents said this was not enough.

"They will have a small impact but this is not really what we wanted," said Du Xuelian, a clerk in a shop selling eyeglasses in Urumqi.

"We want them to solve these problems. Changing officials isn't really the answer."

The protests in Urumqi began on Wednesday with angry citizens demanding the government act to stop a spate of mysterious syringe attacks, just under two months after ethnic riots in the city left nearly 200 mostly Han Chinese dead.

Calm only returned to the northwestern city on Saturday.

Liu Jialong, the owner of another glasses shop, called on the new officials to act firmly.

"This (the sackings) will definitely have an impact. But long term, to solve all these problems, it's going to take a lot of time and a lot of effort," he said.

"We hope the new officials will have greater resolve in handling these affairs."

On Sunday, life in Urumqi began to return to normal, with pedestrians and traffic back on the streets.

But in a sign of continued tension, thousands of armed police were spread out in the city, and officers searched the bags of passing men and women in the traditional Uighur district, as plainclothes officials looked on.

"It's really sad to live like this," said a 37-year-old store owner, who refused to be named -- a member of the mainly Muslim Uighur minority.

"We don't know how long it will be before we can relax again."

More than 530 people have gone to hospital after being stabbed with syringes in Urumqi in the past few weeks, official media said, and authorities have stressed that both Han and Uighurs were victims of the attacks.

China has arrested four people in connection with the stabbings, and four others are to be criminally prosecuted.

A statement by law enforcement authorities on Sunday said that the attackers would face harsh punishment and even death if the syringes were found to have passed on poisonous or harmful substances, state news agency Xinhua reported.

Separately, Wang Lequan, Xinjiang's Communist Party chief, said the protests were triggered when four people stabbed a Han Chinese woman with syringes in a shopping area in Urumqi, Xinhua reported.

He said the government would send 600 officials to Han Chinese-populated areas in Urumqi in a bid to ease tensions, Xinhua reported.

"These officials... will go door-to-door to explain policies and solve disputes," Wang was quoted as saying.

Urumqi city prosecutor Udgar Abdulrahman told journalists on Saturday that in one of the stabbing cases, a 47-year-old Uighur man assaulted police with a syringe containing heroin.

In another case, two drug addicts -- an Uighur man and woman -- threatened a taxi driver with a syringe and robbed him, before being arrested.

A panel of medical specialists told reporters it had examined the records of 217 victims and that so far there was no evidence they had contracted diseases related to radioactive substances, anthrax, hepatitis B or AIDS.

Wang said 1,500 officials had similarly been dispatched to communities heavily populated by Uighurs after the July unrest, according to Xinhua.

Tensions between Han Chinese and Uighurs have been high since the July unrest, blamed by China on "separatists," but which Uighurs say was sparked when Chinese security forces reacted harshly to peaceful protests.