Airports in 18 Chinese cities and regions, including Beijing and six Olympic co-host cities, have stepped up their security measures as of Sunday to ensure the safety of the Olympic Games.

Beijing Capital International Airport has started to use explosive-detection devices at the entrances to its three terminals. Police will check all luggage for explosive materials.

All passengers and those who come to pick up or see people off also must undergo security checks at the terminal entrances for flammable and explosive substances.

Zhang Zhi, deputy director-general of the police department at the airport, says the new hi-tech devices are very effective.

"We use test paper to pick up particles on the surface of the luggage, and then the device will determine if they contain minor elements of explosive materials."

Airport authorities urge all passengers to arrive at airports much earlier to leave ample time for security checks and boarding procedures.