Tens of thousands of people are holding a protest in Cairo against Egyptian President Mohammed Mursi who last week granted himself extensive new powers.
Protesters chanted slogans denouncing the president and the Muslim Brotherhood, accusing them of betraying the revolution that ousted Hosni Mubarak last year, the BBC reports.
Ahead of Tuesday's rally, opposition activists clashed with police. A protester, who was in his fifties, died of a heart attack after inhaling tear gas.
Activists later converged on Tahrir Square - the main focus of the revolution that ousted President Hosni Mubarak - for one of the largest demonstrations to date against Mr Mursi.
Protests are also being held in Alexandria and other cities.
On Monday Mr Mursi sought to defuse the crisis by saying the decree granting him new powers was limited in scope.
He told senior judges that the scope of the measure would be restricted to "sovereign matters", designed to protect institutions.
However, his opponents want him to withdraw the measure completely.
The president's decree, known as the constitutional declaration, said no authority could revoke his decisions.