By Michael Bristow
BBC News, Beijing
Security is high in Xinjiang ahead of the Olympics
China has for months been warning that Xinjiang terrorists were planning attacks during the Olympics - fears that now appear well-founded.
One official said recently that China had cracked five terrorist groups and arrested 82 suspected terrorists in the first half of this year alone.
But some experts believe there is only a "medium risk" that Xinjiang terrorists would disrupt the Olympic Games.
Others say the whole terrorist threat has been exaggerated as an excuse to allow Beijing to carry out repression in Xinjiang.
Increase in attacks
Xinjiang, in the far west of China, is home to the Uighur ethnic group, many of whom resent Beijing's rule over the region.
There has been low-level terrorist activity there for a number of years, but this appears to have increased this year ahead of the Olympics.
As early as March, Wang Lequan, Xinjiang's Communist Party chief, suggested terrorists were planning attacks against this summer's Olympic Games.
Ethnically Turkic Muslims, mainly in Xinjiang
Made bid for independent state in 1940s
Sporadic violence in Xinjiang since 1991
Uighurs worried about Chinese immigration and erosion of traditional culture
"There are always a few people who conspire [to] sabotage. It is no longer a secret now," he said, according to China's state-run Xinhua news agency.
That warning seemed to have been borne out.
Earlier this year, China said it had foiled an attack on a passenger plane flying from the Xinjiang capital, Urumqi.
And just last month officials said they had shot dead five members of a group planning a "holy war" in China.
Now Chinese officials seem to be blaming the East Turkestan Islamic Movement for Monday's attack on the Kashgar police station that left 16 dead.
'No credible evidence'
Over recent months, senior Chinese leaders have stressed that security is the main priority for the Olympics.
So how big is the terrorist risk at the Games? Hong Kong-based security expert Steve Vickers, CEO of consultancy International Risk, said there was only a "medium risk".
"There are real problems in Xinjiang, but my assessment is that these people are well-known and have been infiltrated by the Chinese security apparatus," he said.
Others believe China is using the Olympics as an excuse to crack down on ordinary people in Xinjiang.
Speaking before Monday's attack, Rebiya Kadeer, president of the Uyghur American Association, said there was no credible evidence that Uighurs posed a significant terrorist threat.
"I call on the US government and the international community to condemn China's manipulation of terror threats to kill and intimidate Uighurs on the eve of the Olympic Games," she said in a press release.
Ms Kadeer, who herself spent time in a Chinese prison, claims Uighurs suffer a broad range of human rights abuses in Xinjiang.
These are said to include arbitrary detention, torture, religious repression, and the suppression of the Uighur language and culture.
Nicholas Bequelin, an expert on Xinjiang, said this latest incident could drive a wedge between the Uighurs and the Han Chinese, the country's dominant ethnic group.
Over recent decades, many Han people have moved into Xinjiang, which is rich in natural resources.
"My biggest concern is that an incident like this, and the repression that follows, could further polarise the Uighur and Han communities in Xinjiang," said Mr Bequelin, of Human Rights Watch.
"That would be a disaster, because these people have got to live together."