China will beef up security checks at major airports ahead of the Beijing Olympics after the government warned of a rising terrorist threat for the Games, the nation's aviation watchdog said Monday.

Pasengers at the major airports of Beijing, Shanghai and other cities hosting Olympic events will undergo additional security checks before entering the terminals, the Civil Aviation Administration of China said.

"Passengers entering into those airports with explosives, inflammables or explosive articles will be subject to severe punishment in accordance with current laws and regulations," it said in a statement.

Passengers were urged to arrive for flights with enough time to go through the additional checks that will begin on July 20.

Other airports to undergo increased security checks included the cities of Qingdao, Tianjin and Shenyang, where Olympic events will take place, as well as several other airports in northern China, it said.

Extra checks will also be implemented in the Himalayan region of Tibet and at the Urumqi airport in westernmost China's Xinjiang region.

China has alleged that groups in Muslim-populated Xinjiang have been planning attacks on the Olympics, and accused Tibetans of trying to sabotage the Games.

However human rights groups have accused the government of fabricating or exaggerating threats as an excuse to crackdown in dissent in those sensitive regions.

The new security checks were announced after China's vice chief of police Yang Huanning last week urged security agencies to step up surveillance on hostile forces who may seek to sabotage the Olympics, which start on August 8.

China this year issued new visa rules in an effort to increase security ahead of the Games, measures which tourists and businesspeople have complained make it harder to visit the nation.