"The American Embassy in Islamabad has received threat information regarding possible terrorist attacks against locations in Islamabad in late December, especially during the Christmas and New Year's holiday period," the embassy said.
"Possible targets include places of worship and shopping centres," it said.
The embassy in a statement yesterday has advised American citizens to exercise particular caution during the holiday season and at holiday festivals or events.
"US citizens are reminded to review the active travel warning for Pakistan, and minimize the number and duration of trips to public markets, restaurants, hotels, places of worship, and other locations where large numbers of people congregate," the warning said.
American government personnel are under additional movement restrictions.