The gunfire marks an escalation of tensions, which began on Wednesday when supporters of embattled president Hosni Mubarak charged into Tahrir Square - some on horses and some on camels - clashing with pro-democracy demonstrators gathered there.Protesters from both sides fought pitched battles in Tahrir Square, the epicentre of ongoing demonstrations against Hosni Mubarak, which entered their tenth day on Thursday.

Pro-Mubarak supporters also threw Molotov cocktails and homemade bombs at opposition protesters, who erected makeshift barricades around the square. Our online producer there visited an ad hoc 'prison' where protesters had captured around six pro-Mubarak supporters.The Egyptian army reportedly also arrested several people following the violence early on Thursday, however the numbers were unconfirmed.Hillary Clinton, the US secretary of state, condemned the "shocking" bloody clashes that rocked Cairo, in a call to Vice President Omar Suleiman."The secretary urged that the government of Egypt hold accountable those who were responsible for violent acts," the state department said in a statement.