Issam al-Aryani, the deputy leader of the Brotherhood’s political wing, made an appearance at a rally – near a mosque in Cairo – which was attended by thousands of backers of ousted Islamist President Mohammed Mursi.
The Egyptian army ousted the president on Wednesday and scrapped the Islamist-drafted constitution.
Aryani told the crowd that the Muslim Brotherhood – from which Mursi hails – rejected the removal of the president and will not cooperate with the military-backed authority.
"We will never accept this coup against legitimacy,” he said. "No honorable person will deal with this.”
He also attacked the interim head of state for issuing a decree dissolving the upper house of parliament – the Shura Council.
The Muslim Brotherhood official called on the party’s supporters to continue protesting and "stay in the squares.”
Egypt’s MB leader makes an appearance
Meanwhile, the leader of Egypt’s Muslim Brotherhood, Mohamed Badie, was attending the protest rally in Cairo after reports that he was arrested.
The prosecutor’s office ordered Badie’s arrest on Thursday following the overthrow of Mursi. Security forces said he was detained, but the Brotherhood later denied that.
"Our revolt is peaceful and will stay peaceful, and our demonstrations are stronger than bullets and tanks,” Badie told the crowd. "The people of Egypt will stay committed to their revolution calling for justice.”
He also urged the army not to fire on its own citizens following reports that three pro-Mursi demonstrators were killed in Cairo near the Republican Guard headquarters.
"O, the great army of Egypt, we protect your back and you protect us from our enemies, so don’t shoot at your people,” he said, adding that people of Egypt "will no longer know military rule.”