At least one person has been killed in a blast outside the US embassy in the Turkish capital, Ankara, with reports that it was a suicide bomber.
Dozens of ambulances and fire engines rushed to the scene after the explosion, in an area which is home to diplomatic missions.
According to Turkish broadcaster NTV, the explosion caused no damage inside the embassy itself.
There were no reports of any group saying it had carried out the attack.
The AP news agency quoted police as saying two people had been killed in a suicide attack and NTV said two security guards at the entrance had died.
A number of illegal groups ranging from Kurdish separatists to leftist and Islamist militants have launched attacks in recent years in Turkey, which is a member of NATO.