The largest Opposition rally seen since Mursi assumed power was staged in Cairo’s iconic Tahrir square, the center of last year’s popular uprising that eventually toppled Hosni Mubarak.

Media reports indicated that at least 200,000 people took part in the rally chanting, “The people want the regime to fall.”

One person has been killed and hundreds injured according to Al Jazeera.

In other cities, protesters clashed with the president’s supporters, and stormed or set fire to the local headquarters of the Muslim Brotherhood or its political party, the Freedom and Justice Party, in several cities and towns. Although the Brotherhood had earlier planned to hold its own rallies supporting Mursi on Tuesday, it later called it off to avoid “public tension.”

Egypt has been witnessing violent protests since Mursi issued the controversial declaration last Thursday, in which would shield his decisions from legal challenge until a new parliament is elected.

His decree also protects the Islamist-dominated Constituent Assembly tasked with drafting the country’s first post-revolution constitution from dissolution.

“Egypt is in serious need of judicial reform but decreeing that the president rule by fiat is no way to achieve it,” said Sarah Leah Whitson, Middle East and North Africa director at Human Rights Watch. “Egypt’s president now has more power than last year’s military rulers who used their position to violate human rights. And President Mursy has exempted himself from any independent judicial review.”