The Muslim Brotherhood has called for a week of protests across Egypt to start a day after more than 100 people were killed when security forces fired on protesters staging a "day of rage" against the military-led government.
Undeterred by the bloodshed since Wednesday, in which over 600 people have been killed, the Brotherhood urged its supporters back onto the streets to denounce the overthrow of deposed president Mohamed Morsi and a crackdown on his supporters.
"Our rejection of the coup regime has become an Islamic, national and ethical obligation that we can never abandon," said the Brotherhood, which has accused Egypt's military of plotting the downfall of Morsi last month to regain the levers of power.
Many Western allies have condemnded the killings, including the United States, but Saudi Arabia threw its weight behind the government on Friday, accusing the Muslim Brotherhood of trying to destabilise Egypt.
Violence erupted across Egypt again on Friday after the Brotherhood and other groups, under the banner of the Anti-Coup Alliance, called for protests in defiance of a military crackdown on sit-in demonstrations that left hundreds dead on August 14.
In the worst of Friday's violence, at least 95 people were killed and hundreds injured in Cairo's Ramses Square as anti-coup protesters were fired on by government forces. A correspondent for Al Jazeera described lines of bodies in a makeshift morgue in the nearby Al-Fath mosque.
Egyptian police arrested over 1,000 alleged supporters of the Muslim Brotherhood throughout the day, the interior ministry said in a statement, including 558 in Cairo alone.
Early on Saturday morning, a tense stand-off continued at the Al-Fath mosque. Witnesses inside the building told Al Jazeera that police, soldiers and "thugs" in plain-clothes were attempting to storm the building and that there were hundreds of people inside, including women and children.
Government defends actions
An interim cabinet, installed by the army after it removed Morsi during rallies against his rule, has refused to back down in the face of the protests. It has authorised police to use live ammunition to defend themselves and state installations.
Government spokesperson Bader Abdel Atty defends security forces' crackdown on protests
Bader Abdel Atty, a spokesman for the Egyptian foreign ministry, defended the actions of the security forces in an interview with Al Jazeera, saying that protesters were armed with machine guns.
"They are raising al-Qaeda flags in the heart of Cairo. They are using machine guns against civilians. And this cannot be described as far as I know as a peaceful demonstration," he said.
He dismissed international condemnation of the violence and said Egypt would accept no external interference.
With no compromise in sight, the most populous Arab nation - which is often seen as leading events in the entire region - looks increasingly polarised and angry.
A number of tour operators have suspended all holidays to Egypt until at least next month and the United States has urged its citizens to leave the country.
The European Union asked its states to consider "appropriate measures" to take in reaction to the violence, while Germany said it was reconsidering its ties.