SHANGHAI, June 7 -- MILLIONS of students across China picked up their pens today to start national college entrance exams amid concerns about sweltering temperatures and high-tech cheating.

A record 10 million high school students are sitting the National College Entrance Exam, commonly known in China as "gaokao," for up to four days, vying for about half that number of university places, Reuters said.

Scrapped in 1966 in the educational system, the exams have been credited as the backbone of China's blistering reform-era growth since being reinstated in 1977.

In traffic-clogged Beijing, home to many of the countries top universities, roads near exam venues have been closed to ensure students arrive on time and nearby hotels have been booked out by parents, many of whom will sweat outside in temperatures tipped to exceed 36 degrees.

Air traffic controllers in Anhui province ordered a plane bound for Huangshan city to divert elsewhere this afternoon, due to parents' concerns for their children's concentration during an English language comprehension test.

The nation's papers today printed impassioned editorials urging students to resist the urge to cheat.

Authorities in northeast Liaoning province spent 100 million yuan (US$13.10 million) fitting over 8,000 exam halls with metal detectors and cameras to prevent tech-savvy students from cheating on national college entrance tests.

"Mobile phones, electronic dictionaries, walkie-talkies and pinhole cameras have raised the attention of educational authorities. This year has even seen the manufacture of cheating shoes," the People's Daily said.

Police had found some 42 pairs, selling for about 2,000 yuan each, in a flat in Shenyang, capital of Liaoning Province, the paper said, adding that they -- along with "cheating wallets" and hats -- had proven popular.

Exam supervisors had also been charged with ensuring that no devices, whether concealed in wrist watches or underwear, would escape the dragnet, the paper said.

Some media reported nutritionists prescribing exam-friendly diets and parents scrambling to find attention deficit disorder drugs to give their children an edge.

In Sichuan, some candidates even visited a hospital to get a session of breathing pure oxygen in the hope of enhancing their concentration.