Egypt's army-backed government warned supporters of ousted President Mohammed Morsi Thursday to abandon their protest camps in Cairo, promising them a safe exit if they gave up without a fight.
Police called on Morsi backers to end their sit-ins in two Cairo areas. The Interior Ministry said it had started taking necessary measures to end the vigils in the area of Rabaa al-Adawiya in eastern Cairo and al-Nahda Square south of the capital.
The appeal, made by Interior Ministry spokesman Hany Abdel Latif on state television, followed the government's declaration on Wednesday it was ready to take action to end the protests.
By late Thursday afternoon, army helicopters overflew a sit-in area for about half an hour, a witness told NBC News. He said protesters remained defiant. They had reinforced the area with cement, sand and railroad tracks, but were worried they might come under attack during the night.
Police addressed the protesters on loudspeakers and asked them to leave the square in safety.
Officials also issued a warning to residents around one of the sit-in areas not to accept any strangers in their homes, as the square was being cleared.
Since the army ousted the Islamist Morsi on July 3, police have rounded up many leaders of his Muslim Brotherhood party, mostly on charges of inciting violence. The latest warnings raised the possibility of a potentially bloody showdown.
Latif said that if protesters left the sites peacefully, they would be guaranteed a safe exit, but no deadline was set.
"There is no specified date. We will continue to study the situation on the ground," Latif told Reuters.
Reuters contributed to this report.