Sixteen policemen in China's Muslim-majority northwest were killed on Monday in a suspected terrorist attack, state media said, raising security fears four days before the Beijing Olympics.
In one of the deadliest reported attacks in China in years, two men drove a lorry up to the station in Kashgar city aiming for a group of officers carrying out morning fitness exercises, Xinhua news agency said.
The two got off the vehicle and threw two grenades at the station, moving in to hack at police officers with knives, according to the agency.
Fourteen officers died on the spot, and two others lost their lives on the way to hospital, it said.
Both attackers were arrested, one of them with a leg injury sustained during the raid, according to Xinhua.
"The raid... was suspected as a terrorist attack," the agency said, citing local police.
The incident threw a shadow over the Olympic countdown, after repeated warnings in recent months from the Chinese government that militants from the restive Xinjiang region were planning to stage attacks to wreck the Games.
The Beijing Olympic organisers said it did not know yet if there was a direct connection to the showpiece sporting event, which begins on Friday.
"We have to check," spokesman Sun Weide told AFP when asked if there was any link to the Olympics.
International Olympic Committee spokeswoman Giselle Davies told AFP the IOC had no immediate comment on the incident but expressed confidence authorities were doing all they could to provide a safe and secure Games.
In line with the flow of information in China surrounding security issues, reports were released only through official channels, while local authorities denied any knowledge of the event.
"We don't have any information about it. We have not heard of this matter," a police spokesman in Xinjiang's capital Urumqi said when contacted about the initial report. He declined to give his name.
"Everything has returned to normal," an official with the Kashgar People's Armed Police said by telephone. He declined any other comment.
China has warned repeatedly of a major terrorist threat emanating from Xinjiang.
"The Beijing Olympics is facing a terrorist threat unsurpassed in Olympic history," the People's Daily, the mouthpiece of the ruling Communist Party, said in an editorial last month.
China's state media carry only sporadic reports about violence in Xinjiang, making it difficult to determine the extent of the threat in the region.
Rights groups and members of the ethnic Muslim Uighur population in Xinjiang have accused the government of exggerating the threat as cover to crackdown on all forms of dissent.
However, observers said they believed this could be the deadliest incident of its kind yet.
"If 16 people died, I would think that this is the highest casualty ever reported for an incident," said Nicholas Bequelin, a researcher with Human Rights Watch and an expert on Xinjiang.
Xinjiang, a vast area that borders Central Asia, has about 8.3 million Uighurs, and many are unhappy with what they say has been six decades of repressive Chinese rule.
China has deployed more than 100,000 security personnel to provide security for the Games, which run from August 8-24.
A senior official said last week the main Olympic threats were from the East Turkestan Islamic Movement in Xinjiang, forces seeking Tibetan independence, the banned Falungong spiritual group and overseas pro-democracy forces.