The US has ordered all non-essential government personnel to leave its consulate-general in the Pakistani city of Lahore. A senior State Department official said the move was in response to a "credible threat" to the consulate.
US personnel remaining in Lahore should limit non-essential travel within the country, the official said.
On Thursday, the US issued a travel warning advising all US citizens to defer non-essential travel to Pakistan.
"We are undertaking this drawdown due to concerns about credible threat information specific to the US Consulate in Lahore," the official said.
"An updated travel warning has also been issued," the statement said, adding that "US citizens remaining in Lahore... should limit non-essential travel within the country, be aware of their surroundings whether in their residences or moving about, [and] make their own contingency emergency plans."
The travel warning said: "The presence of several foreign and indigenous terrorist groups poses a potential danger to US citizens throughout Pakistan."
US officials say it is not clear when the consulate will open again.
The US has closed 19 diplomatic missions in the Middle East and Africa this week in response to what it said was a threat of a terrorist attack.
The evacuation from Lahore was undertaken as a precaution and was not related to the closure of the other diplomatic missions, AP news agency reported, citing two unnamed US officials.
The Pakistani authorities have been holding the capital on a state of high alert, especially key Pakistan government installations, the BBC's Charles Haviland in Islamabad, Pakistan's capital, reports.
Britain has travel warnings in place for Pakistan but these are for specific locations not including Lahore or the capital, our correspondent adds. (BBC)