CAIRO - Supporters of Egypt's ousted president Mohamed Morsi pledged to press their protests on Sunday, a day after bloody clashes at a Cairo sit-in killed at least 72 people.
Sporadic violence was reported nationwide overnight, including in the Suez Canal city of Port Said.
Saturday's violence in the capital drew international and domestic condemnation, including from Washington, a key backer of the Egyptian army.
Following the clashes near the Rabaa al-Adawiya mosque where Morsi loyalists have been camped out for weeks, the interior minister pledged to disperse the protests "soon".
But the violence and the warning did not appear to have thinned the ranks at the Cairo demonstration, where a core group of several thousand protesters remained.
And Gehad El-Haddad, a spokesman for the Muslim Brotherhood, said demonstrators were angry but "hugely defiant" after Saturday's deaths.
"There are feelings of agony and anger, but also a very strong feeling of determination," he told AFP.
"People are hugely defiant," he added.
"For us, if we die, we meet our creator and we did so for a just cause... Either we die or we succeed."
The violence early on Saturday was the bloodiest incident since Morsi's July 3 ouster by the military following huge demonstrations against his rule.
The deaths came after rival protests both for and against Morsi on Friday.
The health ministry said 72 people were killed in Cairo on Saturday, along with nine killed in second city Alexandria a day earlier.
Sporadic violence continued overnight, including in Port Said, where state news agency MENA said 15 people were injured during clashes at the funeral of a Morsi supporter killed in Cairo.
MENA and an eyewitness speaking to AFP said Morsi supporters opened fire during the funeral, but a Brotherhood spokesman said the mourners had come under attack.
A medical source at Port Said's Al-Amiri hospital said it had five people wounded in the clashes, "including two in a critical condition, with bullet wounds to the neck and chest".
In Menufiya, in the central Delta region, Morsi opponents set fire to the Brotherhood headquarters, causing no injuries, MENA said.
Funerals for many of the ousted president's backers killed on Saturday were expected to take place on Sunday, raising fears of further violence.
Morsi supporters accused security forces of using live fire against unarmed protesters, but the interior ministry insisted that its forces had only fired tear gas.
Interior Minister Mohammed Ibrahim also warned on Saturday that pro-Morsi demonstrations would be dispersed "in a legal fashion" and "as soon as possible".
He called on protesters to "come to their senses" and go home.
The violence prompted international condemnation.
US Secretary of State John Kerry, whose country contributes hundreds of millions of dollars in military and economic assistance to Egypt, expressed Washington's "deep concern".
In a statement, Kerry called on the authorities to "respect the right of peaceful assembly and freedom of expression".
Turkish Prime Minister Recep Tayyip Erdogan, who has infuriated Egypt's interim administration by maintaining his support for Morsi, denounced what he described as massacres.
British Foreign Secretary William Hague urged the authorities to "cease the use of violence against protesters, including live fire, and to hold to account those responsible".
The violence also prompted domestic criticism, with Vice President Mohamed ElBaradei, a former opposition activist who joined the transitional government, denouncing "excessive use of force" by the authorities.
The head of Al-Azhar, Egypt's top Sunni Muslim authority, also condemned the violence, calling for an "urgent judicial investigation".
But the National Salvation Front, a coalition of leftist and liberal groups, said Morsi's Brotherhood bore some of the blame for its "provocative approach".
The deaths followed a call from army chief General Abdel Fattah al-Sisi, who led the coup that ousted Morsi, for a mass show of support for a crackdown on "terrorism".
Hundreds of thousands of Egyptians obliged, demonstrating their continued support for Morsi's ouster.
The former president, elected after the 2011 uprising that toppled one-timeaa leader Hosni Mubarak, is being held in custody.
He is accused of "premeditated murder" over his escape from prison during the 2011 uprising.