President Recep Tayyip Erdoğan on Thursday urged the U.N. to launch an official investigation into the death of Egypt's first and only democratically elected President Mohammed Morsi.

Speaking to journalists at a media event, Erdoğan said Egyptian authorities did not intervene while Morsi suffered for more than 20 minutes before he fell unconscious, and eventually died.

Morsi reportedly died from a heart attack Monday during a court session. The country's state television reported early Tuesday that Morsi was "suffering from a benign tumor, had continuous medical attention and his death was caused by a heart attack." He was buried in Nasr City, east of Cairo, early Tuesday morning.

"They didn't make the slightest intervention as the country's first democratically elected president suffered for more than 20 minutes. They didn't deliver his remains to his family or let him be buried in his hometown per his will," Erdoğan said, blaming Abdel Fattah el-Sissi for Morsi's death.

"Sissi is a tyrant, not a democrat," Erdoğan said.

"I hope the U.N., which found Turkey's stance on Jamal Khashoggi's murder right, will also handle the suspicious death of Morsi," Erdoğan said.

"We won't allow Morsi's death to be forgotten just as we have not allowed late Jamal Khashoggi's death to be forgotten," he added.

Erdoğan said Turkey would also use every available resource within the confines of international law to shed light onto Morsi's death.

Morsi was elected president in 2012 but was ousted in a military coup a year later. The military, then led by incumbent President Sissi, crushed the Muslim Brotherhood movement in a major crackdown, arresting Morsi and many others of the group's leaders, who have been in prison undergoing multiple trials ever since the coup.

According to his family, Morsi had diabetes and kidney disease and had not been provided with proper medical treatment.

Amnesty International and other rights groups have called for a fair, transparent and comprehensive investigation into Morsi's death and raised questions about his treatment in prison. Egypt's government has dismissed accusations that he was badly treated.