The US State Department updated its travel warning on Turkey on Saturday, ordering family members of consulate employees in Istanbul to leave the country, citing threats against US citizens.
The advisory warns that tourists will be targeted by terrorist organisations in the country and that an attack could occur at crowded places such as tourist sites and transportation hubs.
It also urged US citizens to "review personal security plans, monitor local news for breaking events, and remain vigilant at all times."
"The Department of State made this decision based on security information indicating extremist groups are continuing aggressive efforts to attack US citizens in areas of Istanbul where they reside or frequent," the department said in a statement.
The US Consulate General in Istanbul remains open and the order does not apply to any other US diplomatic posts in Turkey, according to the department.
Saturday's warning updates previous State Department advisories of "increased threats from terrorist groups throughout Turkey."
The department advises US citizens to avoid travel to southeast Turkey and also advises caution on the risks of travelling anywhere in the country.