At least one person was killed when Egyptian riot police stormed Cairo's Tahrir Square to disperse stone-throwing protesters, a health ministry official said.
Police on Tuesday, backed by armoured vehicles, fired tear gas and shots after clashes in the square in order to scatter protesters who had gathered to mark the anniversary of deadly 2011 demonstrations.
One man was killed when he was struck by birdshot during the clashes, head of emergency services Khaled Al Ansari told Al Jazeera.
It was not immediately clear if he was a protester.
At least 16 people are reported wounded in the violence, one with birdshot to his eye.
The crowds were marking the anniversary of 2011 protests against the military, which took power between President Hosni Mubarak's overthrow and his now deposed successor Mohamed Morsi's election in June 2012.
At least 43 people were killed and more than 3,000 wounded in clashes between the protesters and security forces that began on November 19, 2011, just nine months after Mubarak's ouster.
The clashes broke out near the Arab League headquarters at one corner of the iconic square, with the protesters chanting both against deposed Islamist president Mohamed Morsi and the military that overthrew him in July.
The country has been deeply divided between Morsi's supporters and those of the military, but Tuesday's protesters accused both sides of having betrayed the goals of a 2011 uprising that ousted President Hosni Mubarak.
The military government handed power in 2012 to Morsi, a veteran Muslim Brotherhood leader who won Egypt's first freely contested presidential election.
But just one year later the army overthrew him following mass demonstrations against his turbulent single year in power, and installed an interim government ahead of elections scheduled for next year.
Late on Monday, protesters defaced a newly inaugurated monument to those killed in the mass protests that helped unseat two presidents in less than three years.
Hundreds of angry opponents of the army had gathered in Tahrir Square on Monday evening after Prime Minister Hazem al-Beblawi inaugurated the monument.
By Tuesday, the unfinished brick structure had been vandalised and daubed with anti-military graffiti and a symbolic coffin placed on top of it.
"What we need is trials of those responsible (for the deaths in November 2011) and not celebrations,"
Protester, Reni Rafat said.
Facing the protesters in Tahrir Square were supporters of the army carrying posters of its chief General Abdel Fattah al-Sisi.
"With you, Sisi against terrorism," said a badge worn by one of the demonstrators.
Neither the Brotherhood nor the Tamarod movement which organised the mass protests that led up to Morsi's overthrow had called for Tuesday's rival demonstrations.
There was a light police and army presence in Tahrir itself, although the state MENA news agency said that security had been stepped up around nearby government offices and parliament.