Influential Muslim cleric Yusuf al-Qaradawi on Saturday issued a religious decree, or fatwa, urging Egyptians to support overthrown Islamist president Mohamed Morsi who was toppled by the army on Wednesday.
"Their every action is invalid," Qaradawi said of "those who have overthrown the president, suspended the constitution and imposed another president and constitution" on Egypt.
The Qatar-based but Egypt-born cleric published the fatwa on his Internet site.
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He urged "all parties and political groups in Egypt to support correctness and restore President Morsi to his legitimate post".
"Sharia (Islamic law) imposes on all believers allegiance to the elected president, to carry out his orders and conform to his directives."
Morsi "must remain president, and nobody can claim the right to remove him in the name of the people", Qaradawi added.
"I call on all Egyptians, men and women, young and old, rich and poor, Muslim and Christian, liberal and Islamist to join ranks to protect the gains of the revolution" that overthrew Hosni Mubarak in 2011.
Qaradawi, 86, is regular commentator on Al-Jazeera satellite television and has backed the Arab Spring uprisings in Tunisia, Egypt, Libya, and Syria.