Turkish President Recep Tayyip Erdogan has claimed former Egyptian president Mohammed Morsi did not die of natural causes but that he was killed.
During a speech in Istanbul, Mr Erdogan cited as evidence that the deposed Egyptian president allegedly "flailed" in a Cairo courtroom for 20 minutes Monday and nobody assisted him.
The Turkish leader said on Wednesday: "Unfortunately, Mohammed Morsi was on the ground of a courtroom flailing for 20 minutes.
No official there intervened. Morsi did not (die) naturally, he was killed.
Mr Erdogan said Turkey would do everything in its power to ensure Egypt faces trial in Mr Morsi's death.
He also called on the Islamic Cooperation Organisation to "take the necessary action" over Mr Morsi's death.
Egypt has said the UN human rights office is trying to politicise the death of Mr Morsi, who collapsed inside a Cairo courtroom during his trial.
The country's foreign ministry spokesman Ahmed Hafez has denounced as unacceptable comments by Rupert Colville, spokesman for the UN High Commissioner for Human Rights, who called for a "prompt, impartial, thorough and transparent investigation" into Mr Morsi's death.
Mr Hafez said Mr Colville's "politicised and immature" remarks match those from a country exploiting Mr Morsi's death for political purposes, a likely reference to Turkey.
Mr Morsi, who hailed from the now outlawed Brotherhood, was buried on Tuesday.