The latest weapon in the fight against cheating for China's all-important university entrance exam is a six-propeller drone.

The drone flew over two testing centres in Luoyang city in central China's Henan province to scan for any unusual signals being sent to devices smuggled by students taking the annual test.

A Henan province news website said no such signals were detected on Sunday, the first day of the test.

Almost all Chinese high school graduates must take the test, and their scores are the key criterion for which tier of university they can enter.

Luoyang's Radio Supervision and Regulation Bureau said the drone cost hundreds of thousands of yuan (tens of thousands of dollars).