At an election rally in Istanbul, Recep Tayyip Erdogan said Morsi “did not die, he was murdered” and called on the Organisation of Islamic Cooperation to act on his death.
Mr Erdogan said: “Unfortunately, Mohamed Morsi was on the ground of the courtroom flailing for 20 minutes. No official there intervened. Morsi did not [die] naturally, he was killed.”
Friends and colleagues of Morsi have accused security forces of murdering the former president and claim that police failed to administer first aid fast enough when he collapsed.
Prison guards allegedly left the 67-year-old “slumped on the floor” in the courtroom for more than 20 minutes, despite other defendants calling for help.
United Nations’ spokesperson Rupert Colville has called for a “prompt, impartial, thorough and transparent investigation” into Morsi’s death and his detention conditions.
Morsi, who was Egypt’s first democratically elected president, was buried quietly in Nasr City, an eastern suburb of the capital, on Tuesday.