Thousands marched at the funeral procession of Gaber Salah, a member of the April 6 movement known by his nickname "Jika", who was critically injured in clashes near Cairo's Tahrir Square last week and died overnight.
In the Nile Delta city of Damanhour, hundreds turned out for the burial of Islam Fathi Mohammed, a young member of the Muslim Brotherhood who was killed in clashes outside the Islamist movement's offices.
In Cairo, some wept, others chanted for justice as Jika's white coffin was carried from Omar Makram mosque in Tahrir Square -- where activists have been camping out to protest President Mohamed Morsi's assumption of sweeping powers -- towards Mohammed Mahmud street, where violence has been brewing for the past week.
Mourners comforted his devastated mother, as one protester carried a sign that read "Glory for Gaber."
"It isn't acceptable to have such killings now. We refuse all sorts of violence," said longtime activist George Ishak, who attended the funeral.
"What is happening is a warning to Morsi that the country is in danger," he said.
In Damanhour, protesters marched somberly, carrying posters of Fathi, as they prayed for him en masse.
Some blamed members of the regime of ousted president Hosni Mubarak of instigating the violence that led to Mohammed's death.
"The criminals of the old regime were sent to attack," one mourner told Al-Jazeera Egypt, which was carrying the funeral coverage live.
"The only thing Islam did was to protect the office," he said.
Witnesses said clashes had broken out in Damanhour between supporters and opponents of Morsi, during protests there against the sweeping new powers he has assumed, with petrol bombs, sticks and stones being used.
The witnesses said clashes have been going on for the past three days between the Islamists and Morsi's opponents, who have tried to storm the Brotherhood office in the Nile Delta town.
Several offices belonging to the Muslim Brotherhood's Freedom and Justice Party have been torched since Thursday's announcement.
The funerals come on the eve of rival mass rallies in response to Morsi's decree which have given broad powers and place him beyond judicial oversight and which threaten to deepen the country's divisions.