Beijing public security authorities launched three "defence lines" on Tuesday morning to beef up safety checking on people or vehicles to enter the city.

The three lines surrounding Beijing are composed of hundreds of checkposts, said a spokesman for the municipal public security bureau.

The first line includes checkposts on the expressways, national highways and town or village roads that link Beijing with other provinces or cities.

The patrol posts on the second line are stationed on the major suburban roads leading to the downtown area.

The third line covers all major roads in the downtown districts.

On Tuesday, big traffic flows caused congestions on the expressways linking Beijing to Kaifeng, Shenyang and Shijiazhuang, and the National highways No. 103 and No. 107.

To prevent traffic jams caused by the security checks, Beijing public police bureau asked the checkposts to add checking personnel, and take suspicious people or vehicles off the road and hand them over to local police stations as soon as possible.

The bureau spokesman said safety check takes time and congestion is sometimes inevitable. "We hope drivers and passengers' could understand and support us in the coming two months."

(Xinhua News Agency July 16, 2008)