Several foreign embassies have warned of possible threats against Westerners visiting Beijing's popular Sanlitun district around Christmas Day, while the Chinese Embassy in the United States advised its nationals in the US about potential terror-related risks.

The alert was first issued by the US Embassy yesterday morning, saying it had received information of possible threats against Westerners on or around Christmas Day in Sanlitun, which is home to bars, restaurants and high-end shops and is frequented by tourists and foreigners.

"US citizens are urged to exercise heightened vigilance. The US Embassy has issued the same guidance to US government personnel," it added, without elaborating on the threats.

The British Embassy later issued a similar advisory.

"There is a general threat from terrorism but the risk of attacks is higher in the Xinjiang Uyghur Autonomous Region. Although foreigners haven't been specifically targeted, attacks could occur in places visited by foreigners," it added.

The French Embassy reposted the US advisory on its website as it warned French citizens to "exercise utmost vigilance".

The Singapore Embassy also issued a safety warning via SMS, urging Singaporeans to "exercise extra vigilance" when visiting crowded places frequented by foreigners in view of the heightened security risks around the world.

On the part of the Beijing police, they have issued a yellow safety alert, the third-highest in a four-tier system, since Thursday. It is reportedly a common move during festive periods or when they have received intelligence of threats or found suspected explosives.

Citing heightened terror risks, the Chinese Embassy in the US advised citizens in an advisory to monitor safety-related information from US government agencies, avoid places that are sparsely populated or with high crime rates, and to be vigilant of strangers and suspicious characters in crowded places. It also issued a security alert after the Paris terror attacks on Nov 13.

Chinese police have ramped up security in Beijing. Sanlitun saw violence in August when a sword- wielding Chinese man attacked a French man and a Chinese woman. She later died in hospital.

American Tim Calder, 27, who lives near Sanlitun, said he would stay at home.

"Some people may think it's just a rumour and attacks wouldn't happen to them," Mr Calder, who works in an education consultancy firm, told The Straits Times. "But I take it seriously."