President of Turkey Recep Tayyip Erdogan said he will spare no effort to hold Egypt’s authorities accountable for the death of ex-president Mohamed Morsi.

Speaking during the rally in Istanbul, Erdogan said he does not believe that Morsi died a natural death, Hurriyet Daily News reported.

“He was killed,” Erdogan said.

Erdogan urged the Organization of Islamic Cooperation (OIC) to take action.

Morsi, who was charged with espionage, died on June 17 during a court appearance. According to the local media, he died of a heart attack.