On Wednesday, police arrested Magdi Qorqor, secretary general of the Egyptian Independence Party and spokesperson for the Muslim Brotherhood-led National Alliance to Support Legitimacy (NASL).
This is according to Ashraf Omran, a lawyer close to Qorqor.
"Qorqor was arrested at his home in Nasr City at 5am without knowing what he is charged with," Omran told Anadolu Agency. "He is now being held at Nasr City police station."
Omran said he expects Qorqor was arrested because he opposed the current regime in Egypt.
Egyptian authorities have yet to confirm Qorqor's arrest.
On Tuesday, police arrested several NASL leaders, including Magdy Hussein, the party chief, Nasr Abdel Salam, acting chief of Construction and Development Party and others.
NASL considers Morsy's ouster on 3 July 2013 a military coup and the group does not recognize any political steps that took place after that, including President Sisi's election.
However, Morsy's opponents believe the events of 2013 were a popular uprising.
Edited translation from Anadolu Agency