Two former ministers in the era of Mohamed Morsi - the first democratically elected civilian president in Egypt - called for a UN investigation into the death of Abdullah, son of the late president.

This came in a joint statement by the Minister of Planning and International Cooperation Amr Darraj, and Investment Yahya Hamed - who took office during the period (2012/2013) - according to the latter on his Facebook page.

In the statement, the two former ministers welcomed the talk of UN experts on Morsi's death and called for a UN investigation that would include the circumstances of the death of Abdullah, son of the late president.

Hamid said, "I fully support the initiative taken by human rights experts of the United Nations to investigate the death of President Morsi, but to understand the full truth, the United Nations must also investigate the death of Abdullah Morsi."

For his part, Darraj said that the international community has largely failed in the field of democracy in Egypt, and allowed authoritarian regimes to violate international law without accountability. This investigation is an important step forward in holding such regimes accountable for their actions.

He added: Democratic movements in Egypt and the Middle East must know that they will be supported by the international community when authoritarian regimes violate their rights and use criminal acts to suppress them.

Earlier on Friday, UN experts said Egypt's prison system was "responsible" for Morsi's death.

The experts confirmed in a joint statement published on the website of the International Council for Human Rights of the United Nations that Morsi was held in conditions that can only be described as brutality, especially during his detention for five years in the Tora prison complex (south of Cairo).

Experts believe that these conditions directly led to the death of Morsi, and it puts the health and lives of thousands of other prisoners at great risk.

The Egyptian authorities could not be reached for comment on the experts' statement, but they used to deny this, stressing that all actions taken with prisoners "within the framework of the law."

Morsi died during his trial in June after a sudden heart attack, according to Cairo at the time, and his youngest son, Abdullah, died last September in a sudden heart attack as well, according to his family lawyer.