US Secret Service agents arrested a man after he fired a gun outside the Ethiopian embassy in Washington on Monday, US media reported.
Video shown by Ethiopian television ESAT shows a man standing inside the embassy compound and brandishing what appears to be a handgun.
Several people are heard yelling and seen trying to approach the man when a gunshot rings out.
Local media said no one was injured.
A State Department spokeswoman said a man was arrested and that a protest had been taking place near the embassy.
NBC News reported that the alleged shooter was an embassy employee.
It was not immediately known whether the gunman will face any charges or if he will enjoy diplomatic immunity as an employee of the embassy, NBC said.
The Secret Service did not immediately return a call from AFP.
State Department spokeswoman Jen Psaki said her office "takes very seriously any incident involving the use of a firearm."