A court in western China's Xinjiang region sentenced three people to up to 15 years in prison Saturday in the first trials over a series of mysterious syringe attacks that led to mass protests against the local government.

The three, all ethnic Uighurs, were sentenced by the Intermediate People's Court in the regional capital, Urumqi, state media reported.

Some 500 people have reported being attacked in the city, but only about 100 have showed evidence of being pricked. None have suffered from illness, poisoning or other effects.

Earlier this month, tens of thousands from China's ethnic Han majority took to the streets of Urumqi to demand that the government improve security, as the needle attacks raised tensions almost two months after riots left nearly 200 dead and exposed rifts between the native Uighur minority and Han Chinese.

Officials say five people died in the protests and 48 people were detained as suspects in the needle attacks, according to state media.

The court on Saturday sentenced 19-year-old Yilipan Yilihamu to 15 years in prison for inserting a needle into a woman's buttock on Aug. 26, a notice on the official China Court Web site said.

The woman was standing buying fruit by a stall when she was stabbed. She didn't realize until she returned to work after which she told police. The teen was caught four hours later, the Web site said.

State-run China Central Television said the teen was about to start college and had no previous criminal record. The official charge against him was "spreading false dangerous substances," but the TV channel said the prosecution wanted to charge him on the more serious count of endangering public security by dangerous means.

He did not accept his verdict and plans to appeal, the Web site said.

In a separate hearing, the court also sentenced a 34-year-old man, Muhutaerjiang Turdiand, and a 22-year-old woman, Aimannisha Guliwere, to 10 years and seven years, respectively, for robbery after they threatened a taxi driver with a syringe and took 710 yuan ($103) off him on Aug. 29. They were also fined. The two turned themselves in to police, CCTV said.

The official Xinhua News Agency said all three are Uighurs, a mostly Muslim, Turkic-speaking ethnic group that is the largest in Xinjiang at 45 percent of the population. Around 200 people were present at the two hearings, it said.

Officials and state media have blamed both the deadly July rioting and the attacks on Uighur separatists bent on destroying ethnic unity, but have not publicized any evidence to support the allegations.