The 12 suspects were among 20 people for whom detention warrants were issued by the Ankara state prosecutors' office, Anadolu said.
According to the statement, they are suspected of trying to recruit members for the extremist group and were allegedly in contact with people in "conflict zones".
Ankara police have strengthened security measures in the Turkish capital, the Ankara mayor's office said in a message March 5.
No further details about the threat were released by the embassy.
Trump jokes about his impeachment, mocks media
The president also referred to the numerous staff departures from the White House during his first year in office. He added that North Korea had "called up a couple of days ago" to say they would be open for talks.
The United States Embassy in Ankara, Turkey has announced it will not open on Monday.
The U.S. embassy in Turkey's capital Ankara was closed Monday due to an unspecified "security threat" to Americans.
On its website, the mission urged Americans to "avoid large crowds" and "keep a low profile".
Turkish anti-riot police secure the area around the U.S. Embassy in Ankara during a protest against the U.S. president's decision to officially recognize Jerusalem as the Israeli capital, on December 7, 2017. A far-left terrorist group subsequently claimed responsibility for that attack.