BEIJING - China's Ministry of Education on Saturday ordered local authorities to guard against "potential threats" posed by "various unstable factors" in society to ensure security during the ongoing national college entrance examination.

In an urgent circular, the ministry asked officials to cooperate with local police to conduct special security inspections on the exam rooms, examinees' cafeterias, dorms and emergency shelters so as to root out pitfalls.

Special personnel should be designated to take care of vehicles used to transport students to exams, and conduct security checks on all carry-on liquid items, according to the circular.

All flammable and explosive articles as well as irrelevant personnel and items should not be allowed on board, it said.

Approximately 9.12 million people are sitting the exam, the largest exam of its kind worldwide, to vie for access to the country's universities and colleges. The number is 30,000 less than last year.