CAIRO (AP) — Egypt said Wednesday that the U.N. human rights office was trying to politicize the death of former Egyptian president Mohammed Morsi, who collapsed inside a Cairo courtroom during his trial this week.

Morsi, Egypt's first democratically elected president who hailed from the now outlawed Muslim Brotherhood group, was buried under heavy security early on Tuesday, a day after his dramatic collapse and death inside a Cairo courtroom.

Rupert Colville, spokesman for the United Nations High Commissioner for Human Rights, called Tuesday for a "prompt, impartial, thorough and transparent investigation" into Morsi's death on Monday.

Foreign Ministry spokesman Ahmed Hafez denounced Colville comments as unacceptable as he tried "deliberately to politicize the natural death" of Morsi during his trial of espionage charges.

Hafez said Colville's "politicized and immature" remarks match those from a country exploiting Morsi's death for political purposes — a likely reference to Turkey.

Turkish President Recep Tayyip Erdogan, who had close ties with Morsi and his Muslim Brotherhood movement, said Tuesday he did not believe Morsi died of natural causes.

Erdogan repeated his claims on Wednesday, saying during a speech in Istanbul that Morsi allegedly "flailed" in a Cairo courtroom for 20 minutes and nobody assisted him.

"Unfortunately, Mohammed Morsi was on the ground of courtroom flailing for 20 minutes. No official there intervened. Morsi did not (die) naturally, he was killed," the Turkish leader said.

Erdogan, who is a fierce critic to the government of Egyptian President Abdel-Fattah el-Sissi, said Turkey would do everything in its power to ensure Egypt faces trial in Morsi's death. He also called on the Organization of Islamic Cooperation to "take the necessary action" over Morsi's death.

El-Sissi has yet to comment on Morsi's death.

Morsi was elected president in 2012 in the country's first free elections following the ouster the year before of longtime autocrat Hosni Mubarak.

The military toppled Morsi in 2013 after massive protests against his divisive rule and crushed the Muslim Brotherhood in a major crackdown, arresting Morsi and many others of the group's leaders.

During his years in prison, Morsi, who was known to have diabetes, was often held in solitary confinement and was largely barred from receiving visitors. His family was only allowed to visit three times. While in detention, Morsi continued to appear in court on a range of charges.

Egyptian rights groups hoped that Morsi's death will bring attention to the conditions inside prisons in Egypt.

The Arabic Network for Human Rights Information said they "cannot keep silent on the slow killing of opposition prisoners."

Another rights group, the Egyptian Initiative for Personal Rights, or EIPR, said Morsi died of "willful negligence."

His death "is an opportunity to shed light on the health conditions inside Egyptian prisons, particularly prisons housing activists and political detainees," EIPR said.