The clashes broke out when supporters of embattled Egyptian President Hosni Mubarak marched into an anti-regime rally in the square, an AFP correspondent reported.
Thousands of protesters from both sides were in the square, the epicentre of opposition demonstrations now in their ninth day.
Several groups were involved in fist fights, and some were using clubs, an AFP correspondent said.
Opposition activists said that plain-clothes policemen had also entered Tahrir Square.(*)
Editor: Aditia Maruli Radja
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