China's official news agency says three security officers were stabbed to death Tuesday and another was wounded in the restive western Xinjiang region.
The Xinhua news agency said an assailant jumped off a vehicle passing a checkpoint and attacked the officers, then escaped.
The attack is the latest in an upsurge of violence in the mostly Muslim region that started shortly before the Olympic Games under way in Beijing.
On Sunday, at least 11 people were killed in a series of attacks in the region. Attackers set off an explosion at a police station in the city of Kuqa, and Chinese authorities said assailants also targeted supermarkets, hotels and government offices in the region.
Days before the Olympics began, an attack in the Xinjiang region killed 16 police officers and wounded 16 others. Officials said two Uighur men were responsible for that attack.
Officials blame the attacks on militants seeking an independent East Turkestan homeland for Muslim Uighurs.
Chinese officials and regional analysts are playing down the possibility that the attacks pose any threat to the Olympics.