The U.S. Embassy in Beijing is warning of possible threats against Westerners in the city's Sanlitun area on or around Christmas day.
Few details were immediately available, although there were signs of increased police presence in the district, which contains popular nightlife venues and international stores.
The U.S. Embassy urged Americans to exercise heightened vigilance.
Similar warnings were issued by the British and French embassies.
Beijing police said they initiated a "yellow security alert" for shopping malls and supermarkets during the Christmas season.
The official Xinhua news agency says a yellow alert is the second mildest under a four-color alert system, which goes from green, yellow, orange to red in order of severity.
"It means 60 percent of the security personnel in those shopping malls and supermarkets should carry out security checks on suspected personnel, materials and vehicles, according to a government security prevention regulation," the report said.
Some material for this report came from AP.
