Police in the Tunisian capital, Tunis, surrounded a mosque on Monday where a wanted Salafist leader is hiding out.
Abu Yadh is accused of calling for and supporting the violent storming of the US embassy in the city last week.
He heads the Tunisian branch of Ansar al-Sharia, which follows a strictly hardline interpretation of Islam.
The group backed a call on Facebook last Friday to attack the American diplomatic mission. It follows the emergence of the now-infamous anti-Islam film that has sparked demonstrations worldwide.
At least two people died and 28 were wounded in the attack.
Islamist extremists clashed with security forces as they set fire to the embassy’s perimeter and hurled petrol bombs.
The protesters also torched and ransacked the nearby American school, which was closed at the time.