CAIRO (CNN) -- The streets around Cairo's Tahrir Square were again roiled by violent clashes between police and protesters Friday, as crowds gathered to mark two years since the start of the revolution that ousted President Hosni Mubarak.
At least 29 protesters have been treated over the past 12 hours for cuts, broken bones and birdshot injuries, Health Ministry spokesman Khaled El Khatib said.
Six police officers have also been hurt in the disorder near Tahrir Square, the Interior Ministry said.
On a street a few blocks away from the square that leads to the Interior Ministry and other government buildings, police erected a barrier of concrete blocks.
Undeterred, young protesters threw rocks over the barrier at officers stationed there, and police responded sporadically by firing tear gas and blaring sirens.
The numbers making their way toward Tahrir Square grew through the morning.
On January 25, 2011, massive crowds gathered in Tahrir Square to protest Mubarak's regime, resulting in his eventual ouster and two years of upheaval.
-- Journalist Ramy Francis reported from Cairo, and CNN's Laura Smith-Spark wrote in London.
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