Demonstrators armed with stones and petrol bombs clashed with troops wielding truncheons and electric prods in Cairo on Friday, witnesses said, in the worst violence since the start of Egypt's first free election in six decades.
Military police tried to break up a sit-in by pro-democracy activists overnight and anger at their rough tactics erupted into clashes that quickly turned the streets around parliament into a rock-strewn battle zone.
In a pattern of spreading violence that has become a familiar refrain during nine months of army rule since President Hosni Mubarak's overthrow, protesters regrouped in growing numbers as resentment at security forces' tactics grew.
By early afternoon, troops were trying to disperse around 10,000 protesters with truncheons and what witnesses said appeared to be cattle prods that they used to give electric shocks to some of the demonstrators.
Ambulance sirens wailed, reports of beatings of well-known democracy activists buzzed across social media and politicians from Islamists to liberals lined up to condemn the army's heavy-handed tactics.
"Even if the sit-in was not legal, should it be dispersed with such brutality and barbarity?" presidential candidate and former U.N. nuclear watchdog director Mohamed ElBaradei said on Facebook.
A health ministry official said 99 people had been injured in the clashes and five had gunshot wounds.
The sit-in outside the cabinet office was a remnant of far bigger protests last month in Cairo's Tahrir Square and nearby streets that left dozens dead and overshadowed the build-up to the first parliamentary vote since Mubarak's fall in February.
In Friday's disturbances, cars were set alight and part of a state building was torched.
Troops and unidentified men in plainclothes hurled rocks from the roof of one parliament building on protesters who threw stones, shards of glass and petrol bombs.
Demonstrators piled car tires and plastic materials in the street and set them alight to send up plumes of black smoke and block the view of the street from above.
The head of the ruling military council, Field Marshal Mohamed Hussein Tantawi, ordered that everyone injured in the fighting be treated in army hospitals, state television said.