Egypt unrest: Rival groups mark anniversary of clashes
Opponents and supporters of Egypt's military-backed administration have clashed on the second anniversary of bloody anti-government protests.
Police fired tear gas at anti-army demonstrators in Cairo's Tahrir Square. Earlier a memorial there was vandalised just hours after it was unveiled.
More than 40 died in November 2011 as protesters and security forces fought.
The protests were against a military council that had taken over after President Hosni Mubarak was ousted.
The so-called Mohammed Mahmoud battle broke out on 19 November 2011 as protesters rallied against the Supreme Council of the Armed Forces (Scaf).
The violence flared after the security forces dispersed a sit-in organised by families of those killed or injured in the uprising in January and February 2011.
Many demonstrators were shot by the security forces and hundreds were injured.
The Scaf handed over power in 2012 to Mohammed Morsi, a veteran Muslim Brotherhood leader who won Egypt's first democratic presidential election.
Mr Morsi was ousted by the military in July this year following protests against his rule. His supporters say he was deposed in a military coup.
Hundreds of Egyptians gathered on Monday evening in Tahrir Square, where the government has built a monument to commemorate those killed in Egypt's uprising.
But by Tuesday morning protesters chanting anti-military slogans had sprayed the memorial with red graffiti, denouncing both the government and the Muslim Brotherhood.
Protesters sang and played drums in Mohammed Mahmoud Street, while in Tahrir Square others chanted for "freedom".
Supporters of army chief Gen Abdel Fattah al-Sisi, who has promised free and fair elections, also gathered in Tahrir Square.
The rival groups were seen throwing rocks and other items at each other.
Egyptian television also showed Brotherhood supporters gathering elsewhere in Cairo to call for Mr Morsi's reinstatement.
In a televised statement on Sunday, Egypt's interior ministry spokesman Hani Abdel Latif said police would protect the planned rallies on Tuesday, but warned that authorities would deal harshly with anyone who turned to violence, according to the Associated Press.
"The interior ministry offers its condolences to all the martyrs of the revolution whose pure blood was shed to water the tree of national struggle," Mr Latif was quoted as saying.