ISTANBUL — The State Department on Sunday ordered all members of the families of its consulate staff in Istanbul to leave Turkey, citing increased security threats from terrorist organizations.

The department said in a statement that the decision was based “on security information indicating extremist groups are continuing aggressive efforts to attack U.S. citizens in areas of Istanbul where they reside or frequent.”

The order was the second warning for United States citizens in Turkey in less than a week. The State Department previously advised Americans to carefully consider the need to travel to Turkey, warning that American tourists had been singled out as targets by international and domestic terrorist organizations.

Turkey has endured numerous terrorist attacks in the past year. The authorities have held the Islamic State or Kurdish militants responsible for the attacks, as the country grapples with both the spillover from the war in Syria and the renewal of a decades-long conflict with Kurdish insurgents in southeastern Turkey.