The US Consulate in Istanbul said on Tuesday that it had cancelled consular services for Wednesday because of "information about a possible security threat" against the mission.
"We strongly encourage U.S. citizens to maintain a high level of vigilance, be aware of local events, and take the appropriate steps to bolster your personal security," the consulate added in a statement on its website.
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In Washington, State Department spokesman John Kirby told reporters that routine consular services had been cancelled but that limited, urgent services would be provided.
Other US diplomatic missions in Turkey - in Ankara, Izmir and Adana - will operate normally, the statement said. It did not elaborate on the possible threat.