Knife-wielding attackers killed three Chinese security officers and injured another at a checkpoint in the restive western Chinese province of Xinjiang on Tuesday, pushing the death toll from attacks during the Olympic period to more than 30.

Several assailants leapt out of a car at a checkpoint in Yamanya , near the border city of Kashgar, and hacked to death three government employees who were registering travellers’ details, according to state media and officials.