Clashes and confusion broke out in Egypt's Tahrir Square on Friday, with violence leaving at least 100 injured.

Supporters and opponents of President Mohamed Morsi led separate rallies in the capital, according to news agencies.

The Egypt Independent adds:

The fighting marks a dramatic pro-Brotherhood, anti-Brotherhood polarization. Anti-President Mohamed Morsy protesters were chanting "Sell the revolution, Badie (the Muslim Brotherhood supreme guide)," or the occasional "Fuck Morsy," while members of the Freedom and Justice Party chanted, "There are men behind Morsy."

Others chanted slogans related to the recent Battle of the Camel verdict, where all defendants were acquitted and families of the martyrs shouted slogans calling for the toppling of the regime, apparently a suggestion that the ousted Mubarak regime is still ruling the country. They also chanted "People want to purge the judiciary."

Independent journalist Sharif Kouddous reports that the protests weren't really about sides:

Rock throwing standoff continues. Minor injuries. "who's fighting whom?" one asks. Another answers "don't know" twitter.com/sharifkouddous…

— Sharif Kouddous (@sharifkouddous) October 12, 2012

The clashes are so confused. Hardly about pro and anti Brotherhood. Just violence with neither side really knowing who they are fighting.

— Sharif Kouddous (@sharifkouddous) October 12, 2012

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The Guardian has video of yesterday's clashes: