In its advisory, US Embassy said: "The U.S. Consulate General Karachi received a report of a threat directed at high-end hotels in Karachi."

"In response to such threats, the U.S. Embassy and Consulates sometimes place areas such as tourist attractions, hotels, markets, shopping malls and restaurants off-limits to official U.S. government personnel," the statement said.

The Embassy said the U.S. Consulate General in Karachi has temporarily limited visits by official U.S. government personnel to these hotels.

The security alert also urged people to avoid the areas, keep a low profile, and be aware of their surroundings.

The Embassy also urged people to stay alert in locations frequented by tourists/Westerners.

In its general advisory issued on travelling to Pakistan, the US State Department said people to reconsider their plan to visit the South Asian country.

" Reconsider travel to Pakistan due to terrorism and the potential for armed conflict.  Some areas have increased risk," the advisory said.