URUMQI: The syringe attacks in Urumqi, capital of northwest China's Xinjiang Uygur Autonomous Region, were a copy of violent terrorist crimes and not just normal crimes, said a police official late Tuesday.

"The attacks are copies of violent terrorist crimes," said Du Xintao, an official with the regional Public Security Department, at a press conference.

The recent syringe attacks were neither some individuals' practical jokes, nor simple criminal activities, but organized and planned major adverse events, which had disturbed social order and created an atmosphere of fear, Du said.

They were vicious and difficult to prove, said Yan Yuxing, former president of Urumqi Municipal Intermediate People's Court.

Yan said they aimed to unsettle the city's atmosphere. Yan said the crimes could be punished with death.

The regional and municipal government was tackling the crisis. The government had posted guards in public areas like buses, schools and hospitals. The health department was treating victims. No death nor any case which needs anti-virus drugs had been reported, said an official with the regional center of disease control and prevention.

Tens of thousands of people took to the streets of Urumqi to protest and demand security guarantees last week. Five people died and at least 14 people were treated in hospital with injuries during the protests.

By Thursday, hospitals had dealt with 531 victims of syringe stabbings, 106 of whom showed obvious signs of needle attacks. Police have caught 45 suspects, of whom 12 are in police custody.