Beijing, Jun 3 (IANS): China has begin a crackdown on sale of high-tech devices that can be used for cheating as 9.3 million students prepare to take the world's largest standardised test, the national college entrance examination.

Authorities have launched an exercise to prevent the sale of high-tech devices that might be used to cheat in the tests that will be held across the country June 7-9, Xinhua reported.

In the past two months, eight gangs involved in selling devices such as wireless earphones and transmitter-receiver sets that allow their buyers to listen in to answers and cheat in tests have been detained in Jilin province, said Liang Xiangdong, a senior official.

The National College Entrance Examination (NCEE), or "gaokao", is the world's largest standardized test, taken by millions of Chinese students every year.

A string of cheating scandals featuring the use of high-tech devices has cast a shadow over the test, Xinhua said.

Wireless communication devices are used by some students to obtain answers from people outside the examination venues.

In 2009, teachers in Songyuan city were found to be selling wireless devices to students, sparking public outrage.

Dai Jiagan, an official, Thursday said that about 9.33 million people will take the test in 310,000 exam halls across the country.