CAIRO » The Egyptian army deployed tanks outside the presidential palace today following fierce street battles between supporters and opponents of Mohammed Morsi that left five people dead and more than 600 injured in the worst outbreak of violence between the two sides since the Islamist leader’s election.

The intensity of the overnight violence, with Morsi’s Islamist backers and largely secular protesters lobbing firebombs and rocks at each other, signaled a turning point in the 2-week-old crisis over the president’s assumption of near-absolute powers and the hurried adoption of a draft constitution.

Opposition activists defiantly called for another protest outside the palace later today, raising the specter of more bloodshed as neither side showed willingness to back down.

Morsi was in the palace today conducting business as usual, according to a presidential official who spoke on condition of anonymity because he was not authorized to address the media.

Egypt has seen sporadic clashes throughout nearly two years of political turmoil after the ouster of autocratic leader Hosni Mubarak. But Wednesday’s street battles were the worst between Morsi’s supporters and followers and came after an implicit call by the Muslim Brotherhood for its members to go to the palace and evict anti-Morsi protesters who had camped out there.

Unlike Mubarak, Morsi was elected in June after a narrow victory in Egypt’s first free presidential elections, but many activists who supported him have jumped to the opposition after he issued decrees on Nov. 22 that put him above oversight and a draft charter was later rushed through by his Islamist allies despite a walkout by Christian and liberal factions.

Compounding Morsi’s woes, four of his advisers resigned Wednesday, joining two other members of his 17-member advisory panel who have abandoned him since the crisis began.

Six tanks and two armored vehicles belonging to the Republican Guard, an elite unit tasked with protecting the president and his palaces, were stationed this morning at roads leading to the palace in the upscale Cairo district of Heliopolis. The guard’s commander, Maj. Gen. Mohammed Zaki, sought to assure Egyptians that his forces were not taking sides.

"They will not be a tool to crush protesters and no force will be used against Egyptians," he said in comments carried by the official MENA news agency.

The situation was calm this morning, with thousands of Morsi supporters camping outside the palace after driving away opposition activists who had been staging a sit-in there, prompting fierce street battles that spread to residential areas.

"I don’t want Morsi to back down," said Khaled Omar, a Brotherhood supporter. "We are not defending him, we are defending Islam, which is what people want."

Other Brotherhood supporters outside the palace accused opposition protesters of being Mubarak loyalists or foot soldiers in a coup attempt.

"They want to take over power in a coup. They are conspiring against Morsi and we want him to crack down on them," said one, Ezzedin Khoudir. "There must be arrests."

The violence began when the Brotherhood called on its members to head to the presidential palace to "defend legitimacy" and protect it against what a statement termed attempts by the opposition to impose its will by force. In response, thousands descended on the area, chasing away some 300 opposition protesters who had been staging a peaceful sit-in outside the palace’s main gate. Clashes later ensued with the two sides using rocks, sticks and firebombs.

State television quoted the Health Ministry as saying today that five people were killed and 644 injured by beatings, gunshot wounds and tear gas inhalation.

Morsi, meanwhile, seemed determined to press forward with plans for a Dec. 15 constitutional referendum to pass the new charter. The opposition, for its part, is refusing dialogue unless Morsi rescinds the decrees giving him near unrestricted powers and shelves the controversial draft constitution, which the president’s Islamist allies rushed through last week in a marathon, all-night session shown live on state TV.

Mohamed ElBaradei, a leading opposition reform advocate, said late Wednesday that 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.

Wednesday’s violence spread to other parts of the country. Anti-Morsi protesters stormed and set ablaze the Brotherhood offices in Suez and Ismailia, east of Cairo, and clashes broke out in the industrial city of Mahallah and the province of Menoufiyah in the Nile Delta north of the capital.

Rival demonstrations also were held outside the Brotherhood’s headquarters in the Cairo suburb of Moqatam and security officials said senior Brotherhood official Sobhi Saleh was hospitalized in Alexandria after being severely beaten by Morsi opponents. Saleh, a former lawmaker, played a key role in drafting the disputed constitution. The officials spoke on condition of anonymity because they were not authorized to speak to the media.