At least three people have been killed in an explosion on Friday at an entrance to the U.S. embassy in the Turkish capital of Ankara, NBC reported, citing Turkish police.

Initial casualty reports were varied but some indicated as many as four people had been killed, two of whom were security guards.

Among the fatalities was the suspected bomber, whose explosive was detonated at a side entrance to the embassy.

Police immediately cordoned off the area around the embassy as numerous ambulances converged on the site.