"We will always be non-violent and peaceful. We remain strong, defiant and resolved," Brotherhood spokesman Gehad El-Haddad wrote on his Twitter feed. "We will push (forward) until we bring down this military coup," he added.
Police crackdowns on Wednesday defied international appeals for restraint and a peaceful, negotiated settlement to Egypt's political crisis following the military's removal of President Mohamed Morsi last month, prompting international statements of dismay and condemnation.
Security forces struggled to clamp a lid on Egypt after the worst nationwide bloodshed in decades, although a curfew largely held in Cairo overnight.
Pro-Morsi protesters clashed with police and troops who used bulldozers, teargas and live fire on Wednesday to clear out two Cairo sit-ins that had become a hub of Muslim Brotherhood resistance to the military after it deposed Morsi on July 3.
The clashes spread quickly, and a health ministry official said about 300 people were killed and more than 2,000 injured in fighting in Cairo, Alexandria and numerous towns and cities around the mostly Muslim nation of 84 million.
In Ankara, Turkish Prime Minister Tayyip Erdogan called on Thursday for the UN Security Council to convene quickly and act after what he described as a massacre in Egypt.
"Those who remain silent in the face of this massacre are as guilty as those who carried it out. The UN Security Council must convene quickly," he told a news conference.
At the site of one Cairo sit-in, garbage collectors cleared still-smoldering piles of burnt tents on Thursday. Soldiers dismantled the stage at the heart of the protest camp. A burnt out armored vehicle stood abandoned in the street.
The Muslim Brotherhood said the true death toll was far higher, with a spokesman saying 2,000 people had been killed in a "massacre". It was impossible to verify the figures independently given the extent of the violence.
The military-installed government declared a month-long state of emergency and imposed the dusk-to-dawn curfew on Cairo and 10 other provinces, restoring to the army powers of arrest and indefinite detention it held for decades until the fall of autocrat Hosni Mubarak in a 2011 popular uprising.
The army insists it does not seek power and acted Last month in response to mass demonstrations calling for Morsi's removal.
SHI/SHI