An explosion has rocked the US Embassy in Cairo, Egypt, after a man threw an explosive device at a nearby building, sparking chaos in the area.

Following the explosion a warning was issued by the US embassy advising US citizens to "not come to the embassy".

A man has been detained by Egyptian security forces after throwing an explosive device near the US Embassy in Cairo, three security sources told Reuters. 

No casualties have been reported at the moment, one of the sources added. 

The US Embassy confirmed on Twitter they were aware of a "reported incident" and warned people to stay away from the area for their own safety. 

The Embassy also warned public transportation was likely to be disrupted "due to the incident". 

Issuing a warning on Twitter, they said: "We are aware of a reported incident on Simon Bolivar Street in Cairo.

"Please avoid the area and monitor local media for updates".

The US Embassy is located in Simon Bolivar Street, a busy area of Cairo. 

The reason for the explosion is still not known.

Daily Express contributed to this report.