Several attacks have hit major cities in recent months, with the Islamic State (IS) and Kurdish militants claiming responsibility.
The concern is driven by Turkey’s membership of the American-led coalition against IS, with Turkey hosting coalition planes at its Incirlik air base for raids in Iraq and Syria.
Turkey is also conducting its own campaign against Kurdish militants with a ceasefire between the government and the Kurdistan Workers Party (PKK) breaking down last year.
On Saturday, the US embassy in Turkey published an emergency travel warning on its website containing details of areas authorities believe to be most at risk.
"There are credible threats to tourist areas, in particular to public squares and docks in Istanbul and Antalya. Please exercise extreme caution if you are in the vicinity of such areas," it read.
Antalya, located on Turkey’s Mediterranean coast, is a major tourist centre visited by millions of holidaymakers every year.
In addition, the warning comes a day after Israel’s counterterrorism bureau urged all Israelis to avoid Turkey, saying: "There are immediate risks of attacks being carried out in the country, and we stress the threat applies to all tourism sites in Turkey."
