CAIRO: Supporters and opponents of Egypt's President Mohamed Morsi lobbed firebombs and rocks at each other Wednesday as their standoff over his expanded powers and an Islamic-drafted constitution turned violent.

Bloodied protesters were seen being carried away as gunshots could be heard and the fierce political rivals torched cars and set off firecrackers, before riot police were deployed in a bid to end the confrontations.

Ahmed al-Tayyeb, the grand imam of the Cairo-based Al-Azhar, Sunni Islam's highest authority, called for restraint and dialogue, and two of Morsi's advisers resigned over the crisis.

At the heart of the battle is a decree issued by the president expanding his powers and allowing him to put to a referendum the disputed constitution.

His declaration on November 22 has sparked deadly protests and strikes, but Vice President Mahmud Mekki said on Wednesday that the December 15 referendum would go ahead as planned.

Even after the riot police deployed to break up the violence, the rival camps still clashed in side streets near the palace in the upscale Cairo neighbourhood of Heliopolis.

“It's a civil war that will burn all of us,” said Ahmed Fahmy, 27, as the fighting raged behind him.

“This is a failure of a president. He is waging war against his own people,” 56-year-old Khaled Ahmed told AFP near the presidential palace.

The clashes erupted after thousands of people rallying to the call of the Muslim Brotherhood bore down on the palace, tearing down opposition tents and chanting that they would “cleanse” the area.

The two sides threw stones at each other before the secular-leaning opposition protesters, who had besieged the palace in their tens of thousands on Tuesday, escaped into side streets.

Inside the palace, Mekki told reporters the vote “will go ahead on time”.

The opposition, he said, would be allowed to put any objections they have to articles of the constitution in writing, to be discussed by a parliament yet to be elected.

“There is a real political will to respond to the demands of the opposition,” he told journalists.

Prominent opposition leader and former UN nuclear watchdog chief Mohamed ElBaradei said Morsi bore “full responsibility” for the violence and that his regime was losing more legitimacy every day.

He said the opposition, jointly led by former Arab League chief Amr Mussa and ex-presidential candidate Hamdeen Sabbahi, was ready for dialogue on condition Morsi's decree be rescinded.

“We will not sit down for any dialogue without the cancellation of the constitutional declaration,” he told reporters, describing Morsi's regime as “oppressive and autocratic”.

“The revolution did not happen for this. It happened for freedom, democracy and human dignity,” said ElBaradei.

“Morsi must listen to the people, whose voice is loud and clear. There is no legitimacy in excluding the majority of the people.

There is no legitimacy in enabling one group to dominate Egypt,” he said in reference to the Brotherhood, on whose ticket Morsi ran for office.

Earlier rallies converged outside the palace, where hundreds of anti-Morsi protesters had spent the night, forcing the opposition to leave the area.