Opposition protesters in Egypt have clashed with members of the governing Muslim Brotherhood in several towns, leaving scores of people injured.
In Cairo, the protesters ransacked one Brotherhood office, while in Mahalla in the Nile Delta the Islamist movement's headquarters was set on fire.
Riot police fired tear gas as the two sides pelted each other with stones.
Egypt has been rocked by violent protests this year, which have left dozens dead and many more injured.
On Friday, several thousand activists supporters marched to Cairo's Mokattam area to face Brotherhood supporters and police guarding the movement's headquarters.
Clashes erupted soon afterwards, and the riot police had to use tear gas to keep the two sides apart.
Two buses owned by the Islamists were reportedly set on fire.
"We came to the stronghold of the Brotherhood. No more protests in front of the presidential palace because those ruling Egypt are here,'' protester Hamat Awat was quoted as saying by the Associated Press news agency.
Meanwhile, Brotherhood offices were ransacked by protesters in another part of Cairo and also in the second-largest city Alexandria.
In Mahalla, petrol bombs were thrown at the Islamist office, setting the building on fire, the state-run Mena news agency reported.
A number of Brotherhood supporters said they had arrived from neighbouring towns to protect their movement.
The Brotherhood has recently seen several of its officers attacked across the country in protests against President Mohammed Morsi, the Islamist candidate who won last June's elections.
The secular opposition accuses Mr Morsi of seeking to usurp power - a charge he denies.