There has been global condemnation in the wake of reports that Egyptian security forces shot dead dozens of supporters of ousted President Mohamed Mursi.
The Muslim Brotherhood says crowds were fired on as they gathered close to a round-the-clock sit-in taking place in northeast Cairo.
It is claimed that up to 120 people were killed and thousands injured.
US Secretary of State John Kerry said the rights of peaceful demonstrators must be respected. Major European powers also criticised the latest bloodshed.
The deaths came days after the head of the army called for a popular mandate to wipe out what he described as “violence and terrorism.”
Egypt’s interior minister denied that the police opened fire and said the Muslim Brotherhood is exaggerating the death toll.