CAIRO (AP) -- Egypt descended into political turmoil on Wednesday over the constitution drafted by Islamist allies of President Mohammed Morsi, and at least 211 people were wounded as supporters and opponents battled each other with firebombs, rocks and sticks outside the presidential palace.
Four more presidential aides resigned in protest over Morsi's handling of the crisis, and a key opponent of the Islamist president likened Morsi's rule to that of ousted authoritarian leader Hosni Mubarak.
Both sides were digging in for a long struggle, with the opposition vowing more protests and rejecting any dialogue unless the charter is rescinded, and Morsi pressing relentlessly forward with plans for a Dec. 15 constitutional referendum.
"The solution is to go to the ballot box," declared Mahmoud Ghozlan, a spokesman for Morsi's Muslim Brotherhood, asserting the charter was "the best constitution Egypt ever had."
The clashes outside the presidential palace in Cairo's Heliopolis district marked an escalation in the deepening crisis. It was the first time supporters of rival camps fought each other since last year's anti-Mubarak uprising, when the authoritarian leader's loyalists sent sword-wielding supporters on horses and camels into Cairo's Tahrir square in what became one of the uprising's bloodiest days.
The large scale and intensity of the fighting marked a milestone in Egypt's rapidly entrenched schism, pitting Morsi's Brotherhood and ultra-conservative Islamists in one camp, against liberals, leftists and Christians in the other.
The violence spread to other parts of the country later Wednesday. Anti-Morsi protesters stormed and set ablaze the Brotherhood offices in Suez and Ismailia, east of Cairo, and there were clashes in the industrial city of Mahallah and the province of Menoufiyah in the Nile Delta north of the capital.
Compounding Morsi's woes, four of his advisers resigned, joining two other members of his 17-member advisory panel who have abandoned him since the crisis began.
Mohamed ElBaradei, a leading opposition reform advocate, said Morsi's rule was "no different" than Mubarak's.
"In fact, it is perhaps even worse," the Nobel Peace Prize laureate told a news conference after he accused the president's supporters of a "vicious and deliberate" attack on peaceful demonstrators outside the palace.
"Cancel the constitutional declarations, postpone the referendum, stop the bloodshed, and enter a direct dialogue with the national forces," he wrote on his Twitter account, addressing Morsi.
"History will give no mercy and the people will not forget."
The opposition is demanding that Morsi rescind the decrees giving him nearly unrestricted powers and shelve the controversial draft constitution the president's Islamist allies rushed through last week in a marathon, all-night session shown live on state TV.
Speaking at NATO in Brussels, U.S. Secretary of State Hillary Clinton said the unrest shows the urgent need for dialogue between Morsi's government and opposing voices on a constitutional path going forward.
"We call on all stakeholders in Egypt to settle their differences through democratic dialogue and we call on Egypt's leaders to ensure that the outcome protects the democratic promise of the revolution for all of Egypt's citizens," she said.
The huge scale of the opposition protests has dealt a blow to the legitimacy of the new charter, which Morsi's opponents contend allows religious authorities too much influence over legislation, threatens to restrict freedom of expression and opens the door to Islamist control over day-to-day life.
In addition, the country's powerful judges say they will not take on their customary role of overseeing the referendum. Zaghloul el-Balshi, secretary general of the state committee organizing the referendum, said on the private Al-Hayat television that he would not go ahead with preparations for the vote until the fighting stopped and Morsi rescinded his decrees.
The country's new attorney general, a Morsi appointee, hit back, ordering an investigation of Ahmed El-Zind, chairman of the judges' union that is spearheading the call for a boycott.
Wednesday's clashes began when thousands of Morsi's Islamist supporters descended on an area near the presidential palace where some 300 of his opponents were staging a sit-in. The Islamists, members of Morsi's Muslim Brotherhood, chased the protesters away from their base outside the palace's main gate and tore down their tents.
The protesters scattered into side streets, where they chanted anti-Morsi slogans as the Islamists shouted, "The people demand the implementation of God's law!"
After a brief lull, hundreds of Morsi opponents arrived and began throwing firebombs at the president's backers, who responded with rocks. The clashes continued well after nightfall and spread from the immediate vicinity of the palace to residential streets nearby.