Clashes between protesters and Egyptian security forces intensified after nightfall Monday, marking the anniversary of a bloody confrontation in Cairo, when 42 people were killed in a street battle months after the uprising that ousted the country's longtime president.
Hundreds of demonstrators threw rocks at police, who fired tear gas and birdshot in response. A medical official said 60 protesters and 10 policemen were injured. He spoke on condition of anonymity because he was not authorized to brief reporters.
The clash was a small scale reprise of one of the fiercest confrontations after last year's popular revolution, when the protesters who brought about the overthrow of longtime President Hosni Mubarak returned to the streets to demonstrate against the harsh measures imposed by the military, which took over from the ousted leader.
The persistent unrest reflects divisions plaguing Egypt 21 months after Mubarak's downfall in February 2011. While young, mostly secular activists spearheaded the uprising, the main winners in the aftermath have been fundamentalist Islamic movements — the Muslim Brotherhood, which won elections for parliament and president, and the more extreme Salafis, who have also shown considerable electoral strength.
That has left the frustrated liberal activists on the outside, demonstrating against both the military and the Brotherhood.
On Monday, protesters tore down a cement block wall between Cairo's downtown Tahrir Square, the focus of huge demonstrations last year, and the headquarters of the security forces.
While the casualties were lower, many of the scenes were almost eerily the same as a year ago.
Protesters riding motorbikes rushed the injured to a field hospital. Others carried pictures of demonstrators killed in last year's crackdowns by the military.
Demonstrators hung a banner read, "Muslim Brotherhood not allowed," while others chanted, "the people want to topple the regime," referring to Islamist President Mohammed Morsi, whose Muslim Brotherhood avoided street confrontations with the military rulers last year to focus instead on campaigning and elections.
Protester Abdullah Waleed said the protest was aimed at opening main roads that have been blocked for a year.
"While we were tearing down the cement blocks, security forces fired at us," he said. "I was wounded by (shotgun) pellets."
Last year's street battle, known as "Mohammed Mahmoud" after the name of the street where it unfolded, was triggered by a security crackdown on a sit-in by injured protesters. It set off days of sustained violence, with security forces firing tear gas, shotgun rounds and rubber bullets, wounding hundreds.
Rights groups and protesters have demanded retribution for the deaths in this incident and others.
In a report Monday, Human Rights Watch report said bringing those responsible for killing protesters to justice is a "key test" of Morsi's pledge to carry out reforms and hold police accountable.
"Mohamed Mahmoud is a major example of impunity for police violence against protesters," the group said, noting acquittals of police officers in cases related to killing of protesters.
"Since January 2011, the police have been literally getting away with murder, again and again," said Nadim Houry of HRW.
The tensions have not disappeared since the military relinquished power at the end of June, as evidenced by Monday's bitter confrontations.
Even members in different security forces battled each other.
An Egyptian security official said clashes erupted between civilian police and military forces in northern Cairo after police arrested a military officer over a traffic violation. Hundreds of soldiers encircled the police station where the officer was being held, trying to storm the station, while the police fired tear gas to disperse them, the official said.
The incident reflected a feeling among many that the military is acting as a state within a state. The official spoke on condition of anonymity because he was not authorized to speak to reporters.
The violence comes during tensions over the writing of Egypt's new constitution. Members of several liberal parties and representatives of Egypt's churches have announced their withdrawal from the 100-member constituent assembly tasked with writing the document, protesting what they perceive as attempt to impose ultraconservative Islamist content.
Liberals fear that would be the first step toward strict implementation of Islamic Shariah laws, endangering civil liberties, as well as the rights of minorities and women.
Also Monday, authorities arrested another member of Mubarak's regime on charges of using his position to accumulate wealth. The Justice Ministry ordered Monier Thabit, brother of Mubarak's wife, held for 15 days. A large number of associates of the ousted ruler face similar charges.