CAIRO
The National Alliance for the Defense of Legitimacy, a coalition of largely Islamist parties and figures supportive of ousted President Mohamed Morsi, has demanded an international investigation into the killing of tens of pro-Morsi detainees earlier Sunday.
"We expressed our deepest sorrow for the killing of 52 anti-coup detainees," the alliance said.
It was not immediately clear the source for the death toll used by the alliance.
A security source earlier told the Anadolu Agency that at least 37 Muslim Brotherhood detainees were killed in what the Interior Ministry described as an attack on a police vehicle moving Islamists to a jail in northern Cairo.
The Interior Ministry said the detainees have died because of "gas inhalation and stampede".
The pro-Morsi alliance accused the army-backed interim authorities of "a systematic violence against and cold-blooded murder of anti-coup protesters."
Morsi supporters describe as "military coup" his removal by the powerful army on July 3 following mass protests against his regime.
"We hold the leaders of the coup, particularly army chief Abdel-Fattah al-Sisi and Interior Minister Mohamed Ibrahim responsible for this crime and demand an international probe in this and other crimes perpetrated by them."
Earlier, Mokhtar al-Ashri, the head of the legal committee at the Brotherhood's Freedom and Justice Party, accused the authorities of "liquidating" the detainees.
"The Interior Ministry is in this way liquidating anti-coup protesters," he told the Anadolu Agency.
Earlier, the Interior Ministry said a number of Muslim Brotherhood members, remanded into custody, attempted to escape while being moved to jail.
In a statement published on its website, the ministry said the Brotherhood members were being moved from downtown Cairo to Abu Zaabal prison complex in the north.
It accused the members of holding a police officer, adding that security troops were working to free him.
The statement did not specify the number of the Muslim Brotherhood members, the accusations leveled against them nor the circumstances surrounded the reported detention of the police officer.
