April 6 Youth Movement has vowed to take "legitimate" action after its members were attacked during a protest in Mansoura in the Nile Delta on Saturday.
"Thugs with knives and sticks told our members to evacuate the square within five minutes," the group said.
The protesters refused and the resulting violence left many people injured.
On Saturday, the April 6 Youth Movement commemorated the fifth anniversary of a historic strike in Mahalla with anti-government protests in Cairo and a number of other governorates.
The initially peaceful situation in Cairo deteriorated when security forces inside the High Court building fired teargas volleys at the crowds gathered outside.
April 6 Youth Movement had announced earlier in the week that it would celebrate the anniversary with protests against the government of Mohamed Morsi, who members argued had failed to deliver on the promises of the revolution.
Other opposition parties, including the Constitution Party, the Strong Egypt Party, the Revolutionary Socialists and the Free Egyptians Party also took part in the protests.