China is promising a safe and peaceful Summer Olympics, despite a deadly attack on police officers in the country's northwest.
A spokesman for China's Olympics committee is assuring athletes and spectators arriving in Beijing for the Olympics that they will be safe from terrorists.
Tens of thousands of police were on alert across Beijing Tuesday as the Olympic torch arrived in the capital ahead of Friday's opening ceremony.
Authorities also have increased security in the far western Xinjiang region, where 16 police were killed in a knife and bomb attack Monday.
Chinese state media say authorities have detained two men from a mainly Muslim ethnic group for their role in the attack.
Chinese authorities have linked the violence to the East Turkistan Islamic Movement, a group dedicated to gaining Xinjiang's independence.
The group has not claimed responsibility for the attack.
Muslim Uighurs in Xinjiang have been waging a low-level rebellion against Chinese rule for years. Human rights advocates and Uighur groups say Chinese authorities often use terrorism as a pretext to persecute the country's Muslim minority.
Chinese authorities say the East Turkistan Islamic Movement has been planning attacks ahead of the Olympics.
Another challenge facing the Beijing Olympics is air pollution.
Members of the U.S. cycling team arrived in Beijing Tuesday wearing face masks, showing the concern of many athletes that the smog could harm their health and performance.
But the International Olympic Committee's medical commission chief, Arne Ljungqvist, said China's air quality did not pose problems to the athletes or visitors.
Some information for this report was provided by AFP and Reuters.