The United Nations has called for an independent investigation into the death of former Egyptian president Mohamed Morsi.

President Morsi died on Monday aged 67 after collapsing in a Cairo courtroom.

He served as the fifth president of Egypt from 30 June 2012 to 3 July 2013, when he was deposed following mass protests and a military coup.

Morsi was buried on Tuesday morning in a closed funeral ceremony, just a few hours after his death.

“Concerns have been raised regarding the conditions of Mr. Morsi’s detention, including access to adequate medical care, as well as sufficient access to his lawyers and family, during his nearly six years in custody,” said Rupert Colville, a spokesman for the Office of the U.N. High Commissioner for Human Rights. “He also appears to have been held in prolonged solitary confinement.”

Colville’s call amplifies similar calls from the family of Morsi and his supporters.

Egypt’s public prosecutor said a report would be presented later detailing the cause of Morsi’s death.

Morsi has been in prison since he was removed from office, and an organization that he led, the Muslim Brotherhood, has been outlawed.

The former president was sentenced to death alongside 100 other people in May 2015 after being convicted of colluding with foreign militants –Hamas and Shia Islamist Hezbollah movement – to organize a mass prison break. Egypt’s court of appeal however in November 2016 overturned the deaths sentences against Morsi and five other Muslim Brotherhood leaders, ordering a retrial.

(CGTN)