China's official news agency says unknown attackers murdered three security officers in northwestern Xinjiang Tuesday, bringing the death toll from recent violence to 31.

Xinhua reports the assailants jumped off a vehicle passing through a checkpoint, attacked the officers, and then escaped. A fourth security officer was wounded in the attack.

The report says the incident took place in Yamanya town, which is home to many Muslims who are ethnic Uighurs. A spike in violent attacks started shortly before the Olympic Games got underway in Beijing last week.

Officials blame the attacks on militants seeking an independent East Turkestan homeland for Muslim Uighurs.

A representative from the Germany-based World Uighur Congress told reporters in an e-mail that China has recently detained more than 90 Muslim Uighurs in the region.

On Sunday, at least 11 people were killed when attackers set off an explosion at a police station in the city of Kuqa. Chinese authorities said assailants also targeted supermarkets, hotels and government offices.

Days before the Olympics began, attackers killed 16 policemen in the town of Kashgar. The attackers rammed a truck into a group of policemen, then leapt from the vehicle to lob explosives and stab them. Officials said two Uighur men were responsible for that attack.

Chinese officials and regional analysts are playing down the possibility that the attacks pose any threat to the Olympics.

Muslim Uighurs have been waging a low-level rebellion against Chinese rule in Xinjiang for years. Human rights advocates and Uighur groups say Chinese authorities often use terrorism as a pretext to persecute the country's Muslim minority.

 
Some information for this report was provided by AFP, AP and Reuters.