The US Embassy in the Turkish capital Ankara came under brief gunfire early on Monday but nobody was hurt in the incident, which coincides with increased tensions between the two Nato allies over the trial of a US pastor in Turkey.
President Tayyip Erdogan's spokesman condemned the attack as an attempt "to create chaos" and the Turkish Foreign Ministry said it had increased security measures for the embassy and other US missions and employees in Turkey.
An unidentified assailant or assailants fired six bullets at an embassy security gate from a passing white vehicle around 0530 am local time, three bullets hitting an iron door and a window, the Ankara governor's office said in a statement.
The embassy is closed this week for a public holiday to mark the Eid al-Adha festival.
"We can confirm a security incident took place at the US Embassy early this morning. We have no reports of any injuries and we are investigating the details," said David Gainer, the embassy spokesman. "We thank the Turkish National Police for their rapid response."
Video footage from broadcaster Haberturk showed police teams inspecting one of the entrances to the embassy and apparent damage caused by a gunshot could be seen in one window. It said empty cartridges were found at the scene.
Erdogan's spokesman Ibrahim Kalin said the incident was being investigated.
"This is a clear attempt to create chaos," he said on Twitter. "Turkey is a safe country and all foreign missions are under the guarantee of the laws."
The US Embassy in Ankara and the consulate in Istanbul have in the past been the targets of attacks by militants and have faced numerous security threats.
Relations between Turkey and the United States have become increasingly strained in recent weeks, with tit-for-tat tariffs imposed partly due to the trial of a US Christian pastor, Andrew Brunson.
The diplomatic rift has exacerbated Turkey's economic woes, putting additional pressure on the lira currency, which has lost nearly 40% against the dollar since the start of the year.