Enraged Islamists pushed back against the toppling of President Mohammed Morsi, as tens of thousands of his supporters took to the streets vowing to win his reinstatement and clashed with their opponents in violence that killed 30 and wounded more than 200 nationwide.

In a battle Friday on a bridge over the Nile River in Cairo, gunfire rang out and flames leaped from a burning car as rival camps threw volleys of stones and fireworks at each other. Military armoured vehicles raced across the bridge in a counterattack on Morsi's supporters.

The clashes accelerated after four supporters of the president were killed when troops opened fire on their rally — and after a dramatic appearance by the supreme leader of Morsi's Muslim Brotherhood. He defiantly proclaimed that his followers would not give up street action until the return of the president, swept out of power days earlier by the military.

"God make Morsi victorious and bring him back to the palace," Mohammed Badie proclaimed before cheering supporters at a Cairo mosque in his first appearance since the overthrow. "We are his soldiers, we defend him with our lives."

Badie, a revered figure among the Brotherhood's followers, spoke Friday before a crowd of tens of thousands of Morsi supporters in Cairo.  Just released from detention, he had been taken into custody by security forces soon after the military ousted Morsi, who hails from the Brotherhood.

He called on Egyptians to protest, saying "we will not be deterred by threats or detentions ... or the gallows."

Later Friday, the Brotherhood faced another setback when an Interior Ministry spokesman said the deputy head of the Muslim Brotherhood, Khairat el-Shater, had been arrested.

Spokesman Hani Abdel-Latif says el-Shater and his brother were arrested late Friday in an apartment in eastern Cairo on allegations of inciting violence against protesters in recent days.

El-Shater, a wealthy businessman, is the deputy of the Brotherhood's supreme leader, but has long been considered the group's most powerful decision-maker. He was the group's original candidate for the presidency but was disqualified because of a past prison sentence.

Col. Ahmed Ali, a spokesman for the armed forces, said the Muslim Brotherhood was trying to "pick a fight" with the army and "drag it to a clash in order to send a message to the West that what happened in the country is a coup and that the military is cracking down on the peaceful protesters."

That mirrored a statement from an umbrella group of Morsi opponents — including the National Salvation Front and youth groups. The group urged the public to take to the streets immediately "to defend popular legitimacy" against what it called a "malicious plot" by the Brotherhood.

Egyptian troops open fire

Earlier, Egyptian troops opened fire on mostly Islamist protesters marching on a Republican Guard headquarters in Cairo Friday to demand the restoration of Morsi, killing at least one. The shooting came as tens of thousands of his supporters chanting "down with military rule" rallied around the country.

The shooting came when hundreds of Morsi supporters marched on the Guard building, where Morsi was staying at the time of his ouster before being taken into military custody in an unknown location. The crowd approached a barbed wire barrier where troops were standing guard around the building.

When one supporter hung a sign of Morsi on the barrier, the troops tore it down and told the crowd to stay back. A protester hung a second sign and the soldiers opened fire on the crowd, an Associated Press photographer at the scene said. Several protesters fell bloodied to the ground.

At least one had a gaping, bleeding exit wound in the back of his head. Fellow protesters carried the body into a nearby building and covered his head with a blanket, declaring him dead, according to AP Television News footage. Health Ministry official Khaled el-Khatib confirmed that one protester was killed Friday and a number wounded, but he did not know the exact number.

Protesters pelted the line of troops with stones, and the soldiers responded with volleys of tear gas, but the clashes appeared for the moment to ease with mid-afternoon prayers.

CBC's Derek Stoffel, said the army claimed it would only be using tear gas and blank rounds during the incident.

On Friday evening, Stoffel said the environment was "very tense, very dangerous" as opposing protesters clashed.

Stoffel said clashes and unrest are expected to continue into the morning, and possibly in the days ahead.

Crowds in Tahrir Square

CBC's Nahlah Ayed, also in Cairo, said  that the violence is "precisely the kind of incident that was feared today."

She said helicopters have been in the sky all day, shuttling between Tahrir Square and the part of town where pro-Morsi protesters have gathered.

"There are thousands of people still in Tahrir Square … a crowd that has ebbed and flowed throughout the day, depending on what was going on," Ayed said earlier Friday night.

Ayed, who spoke to some Morsi supporters earlier in the day, said the assertion from many of them was that what has happened in Egypt is a military coup, and that outside nations should condemn the change.

"Almost everybody I spoke to maintained that they will remain in that square and several other locations around the country until their president is restored," Ayed said.

Even before the violence she said there was a great deal of anger and emotion on the streets from the Morsi supporters, who feel they have been betrayed. Some of the protesters said they would lay their life down for Morsi, but that they would prefer if the situation remained peaceful, she said.

Militant attack on airport kills soldier

The first major Islamic militant attack came before dawn Friday in the tumultuous Sinai Peninsula, killing at least one soldier. Masked assailants launched a co-ordinated attack with rockets, rocket-propelled grenades and anti-aircraft guns on the airport in el-Arish, the provincial capital of northern Sinai, as well as a security forces camp in Rafah on the border with Gaza and five other military and police posts, sparking nearly four hours of clashes.

One of military's top commanders, Gen. Ahmed Wasfi arrived at el-Arish on Friday to lead operations there as the army declared a "war on terrorism" in Sinai. A crowd of Morsi supporters tried to storm the governor's office in the city but were dispersed by security forces.

The Brotherhood called for Friday's protests, which took place at several sites around the capital and in other cities. Brotherhood officials underlined strongly to their followers that their rallies should be peaceful.

"The old regime has come back … worse than before," said Ismail Abdel-Mohsen, an 18-year-old student among the crowds outside the Rabia al-Adawiya Mosque. He dismissed the new interim head of state sworn in a day earlier, senior judge Adly Mansour, as "the military puppet."

"After sunset, President Morsi will be back in the palace," they chanted. "The people want God's law. Islamic, Islamic, whether the army likes it or not."

Crackdown on Muslim Brotherhood

The military forced Morsi out Wednesday after millions of Egyptians turned out in four days of protests demanding his removal and saying he had squandered his electoral mandate by putting power in the hands of his own Muslim Brotherhood and other, harder-line Islamists. In the 48 hours since, the military has moved against the Brotherhood's senior leadership, putting Morsi under detention and arresting the group's supreme leader and a string of other figures.

On Friday, Mansour dissolved the country's interim parliament — the upper house of the legislature, which was overwhelmingly dominated by Islamists and Morsi allies. The Shura Council, which normally does not legislate, held legislative powers under Morsi's presidency because the lower house had been dissolved. State TV reported Mansour's constitutional decree dissolving the body but did not give further details.

Morsi supporters say the military has wrecked Egypt's democracy by carrying out a coup against an elected leader. They accuse Mubarak loyalists and liberal and secular opposition parties of turning to the army for help because they lost at the polls to Islamists.

But many supporters have equally seen it as a conspiracy against Islam.

Many at Friday's protests held copies of the Qur'an in the air, and much of the crowd had the long beards of ultraconservative men or encompassing black robes and veils worn by women, leaving only the eyes visible. One protester shouted that the sheik of Al-Azhar — Egypt's top Muslim cleric who backed the military's move — was "an agent of the Christians" — reflecting a sentiment that the Christian minority was behind Morsi's ouster.

The protesters set up "self-defence" teams, with men staffing checkpoints touting sticks and home-made body shields. There was no significant presence of military forces near the protests.

In southern Egypt, Islamists attacked the main church in the city of Qena on Friday. In the town of Dabaiya near the city of Luxor, a mob torched houses of Christians, sending dozens of Christians seeking shelter in a police station. Clashes broke out Friday in at least two cities in the Nile Delta between pro- and anti-Morsi demonstrators.

Extremist groups who gained considerable influence during Morsi's year in office have threatened to lash out with a campaign of violence.

A statement released by a spokesperson for UN Secretary-General Ban Ki-moon on Friday cited "worrying reports" of failure to provide due process for people who have been detained, as well as restrictions on freedom of expression.

The statement also expressed concern about the violent clashes that have rippled through the country. Ban called on Egyptian security forces to protect demonstrators and stop violent clashes, but also urged protesters to remain peaceful.

 "The way forward should be determined by the people of Egypt themselves, in a manner that respects the full diversity of Egyptian political views," the statement said.

 "The Secretary-General notes that, for such a process to succeed, there is no place for retribution or for the exclusion of any major party or community."     

With files from CBC News and Reuters