Three people were killed in clashes and 265 arrested in Egypt on Friday in a crackdown on Muslim Brotherhood demonstrations after the movement was labelled a terrorist group, police said.
The military-installed government has banned protests by Brotherhood members demanding the reinstatement of deposed president Mohamed Morsi, after listing the movement as a terrorist organisation on Wednesday.
The three people were killed as opponents of the Islamists clashed with protesters in several cities, the interior ministry said.
Riot police fired tear gas at stone-throwing protesters in several cities, swiftly clamping down on rallies after the midday Friday prayers, the usual time for Islamist demonstrations.
Interior ministry spokesman Hany Abdel Latif accused the protesters of using firearms and petrol bombs, telling AFP they "increased their violence" in Friday's rallies.
The interior ministry said police arrested 265 "Brotherhood elements" in the clashes.
"Legal measures are underway against the Brotherhood elements in accordance with the cabinet's listing of the Muslim Brotherhood as a terrorist organisation," the ministry said in a statement.
The Brotherhood's designation as a terrorist group carries harsh penalties, with the group's leaders facing possible death sentences and protesters looking at up to five years in prison.
Smoke rose from Al-Azhar university's student dormitory in Cairo as police fired tear gas against protesters pelting them with rocks from inside the building, the latest in a series of student demonstrations that have turned violent.
The interior ministry overnight said a man was killed in clashes around Al-Azhar university between Islamist students and civilians who oppose them.
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Protesters wounded several policemen across the country Friday and torched police vehicles, the interior ministry said.
Police seemed intent on hunting down any suspected protesters on Friday, with more than a dozen armoured vehicles racing to a Cairo mosque after reports of Brotherhood members gathering there.
Officers combed nearby buildings searching for suspects and dragged two men out of a car.
The unprecedented decision to blacklist the Brotherhood came a day after a suicide bombing of a police building killed 15 people.
The government blamed the attack on the Brotherhood despite a claim of responsibility from a Sinai-based jihadist group.
Tensions rose even further after a home-made bomb exploded next to a bus on Thursday, wounding five people.
The Brotherhood, which condemned Tuesday's suicide bombing, has denounced its listing as a terrorist organisation and vowed to continue staging peaceful rallies.
It has held near-daily protests since the military ousted Morsi on July 3, despite a crackdown that has killed more than 1,000 people, mainly Islamists, and seen thousands more arrested.
The blacklisting of the Brotherhood as a terrorist group caps a dramatic fall for the movement since Morsi's ouster amid massive protests demanding his resignation following a year of deepening polarisation and plummeting economic conditions.
The Brotherhood renounced violence in the 1970s and has condemned the recent surge in attacks by Sinai-based militants, which have killed more than 100 soldiers and police, mainly in the restive peninsula bordering Israel and the Gaza Strip.
But the interim government accuses the Brotherhood of using violence to derail the transition to elected rule, with a referendum on a new constitution planned for January to be followed by parliamentary and presidential elections.