Supporters and opponents of Egyptian leader Mohammed Morsi fought with rocks, firebombs and sticks outside the presidential palace in Cairo on Wednesday, as a new round of protests deepened the country's political crisis.

Mohamed ElBaradei, a leading opposition advocate of reform and democracy, said Morsi's rule was "losing its legitimacy day after day."

"We're going to continue protesting in every possible way, including a general strike, until we regain our rights and our freedom, and we correct the course of the revolution," the Nobel Peace Laureate told a news conference after he accused the president's supporters of attacking peaceful demonstrators.

The opposition is demanding Morsi rescind decrees giving him near unrestricted powers and shelve a disputed draft constitution that the president's Islamist allies passed hurriedly last week.

The duelling demonstrations and violence are part of a political crisis that has left the country divided into two camps: Islamists versus an opposition made up of youth groups, liberal parties and large sectors of the public.

Both sides have dug in their heels, signalling a protracted standoff.

The latest clashes began when thousands of Islamist supporters of Morsi descended on the area around the palace where some 300 of his opponents were staging a sit-in.

The Islamists, members of Morsi's Muslim Brotherhood group, chased the protesters away from their base outside the palace's main gate and tore down their tents.

The protesters scattered in side streets where they chanted anti-Morsi slogans.

After a lull in fighting, hundreds of young Morsi opponents arrived at the scene and immediately began throwing firebombs at the resident's backers, who responded with rocks.

No casualties were immediately reported but several protesters could be seen with blood streaming down their faces and hands.

Some men were injured so badly they were seen being carried away by fellow protesters.

It was the latest of a series of mass protests against the president.

At least 100-thousand opposition supporters rallied outside the palace on Tuesday and smaller protests were staged by the opposition elsewhere in Cairo and across much of Egypt.

Buoyed by the massive turnout on Tuesday, the mostly secular opposition held a series of meetings late Tuesday and Wednesday to decide on their next steps.

While calling for more mass rallies is the obvious course of action, activists said opposition leaders were also discussing whether to campaign for a 'no' vote in a December 15 constitutional referendum or to call for a boycott.

Brotherhood leaders have been calling on the opposition to enter a dialogue with the Islamist leader.

But the opposition contends that a dialogue is pointless unless the president first rescinds his decrees and shelves the draft charter.

At a meeting held by the opposition coalition, National Salvation Front, Amr Moussa, the former Arab League chief, called on Morsi to cancel the constitutional declaration.

"We are ready for a serious dialogue on the specific basis that he first cancel the constitutional declaration and then seriously deal with the role of the people and their right to discuss and influence the constitution," he said.

Meanwhile, three advisers to President Morsi announced their resignations on Wednesday in protest at his handling of the country's constitutional crisis.

With Wednesday's resignations, five of the president's panel of 17 advisers have quit since the crisis began on Nov. 22, when Morsi issued decrees giving him sweeping powers and putting him above any oversight.