An explosion in Cairo killed four people on Friday (January 24) and wounded dozens.
A group of supporters of General Abdel Fattah al-Sisi gathered at the blast site.
This man said he heard the blast and ran to the scene.
SOUNDBITE) (Arabic) UNIDENTIFIED EYEWITNESS, SAYING:
"Whoever did this must be hanged. I swear, the government's leniency won't do any good in this situation."
Three of the casualties were policemen.
The wounded were rushed to hospital for treatment.
The assault on the Cairo Security Directorate raises concerns that an Islamist insurgency is gathering steam.
It comes a day before the third anniversary of an uprising that toppled Hosni Mubarak.
