US cautions citizens after Delhi attack

"US citizens are urged to always practice good security, maintain a heightened situational awareness and a low profile," a warden message issued by the US said.

"US citizens are advised to monitor local news reports and consider the level of security present when visiting public places, including religious sites," the message said.

"A warden message would be specifically about a general threat, not necessarily to American citizens, but just to keep American citizens in-country apprised of a possible security incident," State Department spokesman Mark Toner said.

"It wouldn't necessarily be a threat to Americans, but just a general matter of concern or issue of concern for security-wise," he said.