An embassy spokeswoman in Ankara today could not provide information on the security threat but said the limited operations would continue through tomorrow.
Last week, the US Consulate in Istanbul warned US citizens to avoid the building due to information about an imminent security threat and suspended consular services for a day.
Unconfirmed Turkish news reports said the Consulate was placed on alert following intelligence about possible plans by Islamic State militants for a suicide attack.
Two massive suicide bombings blamed on a local IS cell killed a total of 130 people in attacks near a town on the Syrian border in July and in Ankara in October.