The Muslim Brotherhood has warned of a "catastrophe" that threatens the lives of 60,000 detainees in Egyptian prisons after the death of former president Mohamed Morsi, who died during his trial on Monday.

The spokesman for the group Talat Fahmy said in a statement that there is "a comprehensive security campaign on the prisons of Egypt," following angry and sad reactions to the circumstances of the death of Morsi, confirming the occurrence of brutal violations in Egyptian prisons.

The statement called on the United Nations and human rights organizations to "speed up the movement and prevent a major disaster against the 60,000 innocent detainees subjected to slow death."

Activists said the prisons were closed after Morsi's death, fearing reactions, and no visits or permission for prisoners to get out of the sport were received before they were gradually opened today.

Cairo routinely denies the existence of political detainees in its prisons, does not announce figures about its imprisonment, and asserts that it guarantees prisoners their rights and provides all their health care.

Morsi died on Monday after six years in prison after military leaders overthrew him in the summer of 2013, after a year in office.

There were many doubts in the circumstances of his death by politicians, parliamentarians, jurists and the UN Human Rights Commission. Some considered them "deliberate killings" because of medical negligence and demanded an international investigation.