Mystery needle attacks appeared to spread in China's far western region as authorities arrested nine new suspects in three cities, officials said Friday.

The suspects were recently detained in the Xinjiang region cities of Hotan, Altay, and Kashgar in connection with alleged attacks involving hypodermic needles, a press officer at the Xinjiang government press center in the provincial capital Urumqi said Friday. He declined to give his name as is customary or provide more details.

Since last week, more than 500 people in Urumqi have reported attacks, though only about 100 showed evidence of being pricked. The bizarre stabbings led to mass demonstrations by tens thousands of Han Chinese earlier this month against what they said was a government that can't guarantee their safety.

The needle assaults have aggravated tensions in the restive western region of Xinjiang where ethnic riots in July left nearly 200 dead. The violence exposed the long-term rifts between Muslim Uighurs, a Turkic-speaking ethnic minority group, and the Han Chinese, who are the majority group in China.

A staffer surnamed Li at the propaganda department of the Communist Party in Kashgar confirmed that people had reported cases but said none showed any evidence of a syringe attack.

"As of now, according to the diagnoses, we haven't confirmed any syringe attacks yet. Most of them only felt some sudden pain when they were walking in the crowd, and some of them felt they'd been tapped on the body. But the doctors and medical examiners did not find any signs of a hypodermic attack on their bodies," he said.

The official China Daily reported out of 19 reported attacks in the three cities, only six were confirmed.

Calls to the city governments in Kashgar, Altay and Hotan were not answered Friday.

Reports of the needle attacks emerged several weeks ago though the size and scale remain unclear. None of the reported victims have suffered from illness, poisoning or other effects. Officials and state media have repeatedly blamed the attacks on separatists bent on destroying ethnic unity.

Rioting in early July by the minority Muslim Uighurs, followed by revenge attacks by Han Chinese, was the worst ethnic unrest in China in more than a decade.

On Friday, two well-known bloggers published accounts of at least two Uighurs being beaten, one of them fatally, last week by Han Chinese, and called on state-run media to provide more balanced reporting of the events.

On his Web site, economist and professor Ilham Tohti — who was detained earlier this year for writing about the reasons behind the ethnic strife in Xinjiang — posted a report on the Sept. 3 beating of local journalist Kaynam Jappar by six or seven Han Chinese men near his home in Urumqi.

In addition, Tibetan writer and blogger Woeser posted on her Web site an account of the beating death of Uighur singer Mirzat Alim, 43, on Sept 2., after being attacked by an armed group near his home.

Calls to the Xinjiang Public Security Bureau rang unanswered. It was impossible to confirm either attack independently.