The order was announced in the second travel warning that the State Department issued for Americans in Turkey in less than a week, reflecting US concerns about "increased threats from terrorist groups."
The decision to evacuate the families of staff was made "based on security information indicating extremist groups are continuing aggressive efforts to attack US citizens in areas of Istanbul where they reside or frequent."
On Monday, the State Department had advised US citizens to "carefully consider the need to travel to Turkey at this time." There is also a long-standing warning against travel to the southeast of the country.
"Foreign and US tourists have been explicitly targeted by international and indigenous terrorist organizations in Turkey," both recent travel warnings said.
President Recep Tayyip Erdogan's government has placed Turkey under a state of emergency in the wake on a July 15 coup attempt by disaffected military officers that triggered a crackdown on suspected dissidents.
Even before the failed but bloody putsch, Turkey was already fighting a renewed insurgency by Kurdish separatists and dealing with the fallout of the war in neighboring Syria, including attacks by the Islamic State group.
In recent months there have been bomb attacks blamed on various groups in Turkish cities, and tensions are running high as Erdogan purges his government of alleged supporters of exiled cleric Fethullah Gulen.
Turkish media have also been stoking anti-American sentiment, accusing Washington of harboring Gulen in Pennsylvania while he allegedly plots the overthrow of Erdogan's government.
The United States has agreed to study an extradition request for the preacher, who denies any link to the coup, but has warned it must meet American "evidentiary standards."
