Tens of thousands of Islamists streamed across a Nile River bridge toward Cairo’s Tahrir Square on Friday, threatening a showdown moments after the top leader of the Muslim Brotherhood defiantly spoke before a cheering crowd of supporters, vowing to reinstate ousted President Mohammed Morsi and end military rule.

His fiery speech, with a military helicopter hovering overhead, came soon after army troops fired on a pro-Morsi rally and one protester was killed.

The dramatic appearance by the Brotherhood’s General Guide Mohammed Badie on stage before tens of thousands of supporters in Cairo was his first in public since the president’s ouster. It injected a further vehemence into the campaign by Morsi’s largely Islamist supporters, who have denounced the military’s removal of Egypt’s first freely elected president as a coup that they will not allow to stand.

Morsi “is my president and your president and the president of all Egyptians,” Badie proclaimed, thrusting his arms in the air. “God make Morsi victorious and bring him back to the palace,” he said in the speech, which was partially aired on state TV. “We are his soldiers we defend him with our lives.”

Badie, a figure revered among the Brotherhood’s followers, addressed the military, demanding they abide by their pledge of loyalty to the president, calling it a matter of the military’s honor. “Your leader is Morsi … Return to the people of Egypt,” he said. “Your bullets are not to be fired on your sons and your own people, you are dearer than that.”

Badie’s speech appeared aimed at not only firing up his supporters but also at trying to win support within the military against army chief Gen. Abdel-Fattah el-Sissi, the defense minister who announced the president’s removal Wednesday night.

Security officials had reported that Badie was taken into custody soon after the military removed Morsi on Wednesday night. Just before Badie’s appearance, the Brotherhood’s political party said on its webpage that he had “been released.” But on stage, Badie denied he was ever arrested. There was no immediate explanation by security officials.

Soon after the speech, Brotherhood backers streamed across a bridge over the Nile River toward the state TV building and Tahrir Square, where hundreds of thousands celebrating Morsi’s fall were massed. There was some stone throwing between the two sides.

Badie’s appearance came three after the military opened fire on pro-Morsi protesters marching on the Republican Guard headquarters in Cairo. The shooting threatened to further escalate Egypt’s confrontation by hiking Islamists’ fury at the military. Already there are fears of an armed Islamist backlash, and before dawn gunmen in the Sinai attacked military facilities, killing one soldier.

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

When one person hung a sign of Morsi on the barrier, the troops tore it down and told the crowd to stay back. A protester put up a second sign, and the soldiers opened fire, according to an Associated Press photographer.

Several bloodied protesters fell to the ground. One had a gaping, bleeding wound in the back of his head. Other protesters carried the body into a nearby building and covered his head with a blanket, declaring him dead, according to AP Television News footage. Witnesses speaking in the footage said men in plainclothes fire the lethal shots.

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. The Brotherhood’s political arm, the Freedom and Justice Party reported five killed, but there was no immediate confirmation. Many of those injured had the pockmark wounds typical of birdshot. The BBC’s Middle East editor, Jeremy Bowen, was hit by birdshot in the head as he covered the clashes. “Am fine,” he reported in a tweet.

Protesters pelted the line of troops with stones, and the soldiers responded with volleys of tear gas. The clashes appeared to ease with the start of midafternoon prayers.

Britain’s Foreign Secretary William Hague said he was “very concerned” by the reports of violence. In a Twitter message, he wrote: “Hope calm heads will prevail, vital to avoid escalation.”

Morsi’s Muslim Brotherhood called for Friday’s protests, which took place at several sites around Cairo and in other cities. Officials of the group strongly urged their followers to keep the rallies peaceful. But the troops’ use of deadly force is likely to fuel calls for violence among harder-line groups that gained considerable freedom to operate during Morsi’s year in office.

The first major Islamic militant attack came before dawn Friday in the tumultuous Sinai Peninsula, killing at least one soldier. Masked assailants launched a coordinated attack with rockets, rocket-propelled grenades and anti-aircraft guns on the airport in the northern Sinai city of el-Arish, where military aircraft are located, 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 night of Morsi’s ouster, jihadi groups held a rally in el-Arish attended by hundreds, vowing to fight. “War council, war council,” a speaker shouted, according to online video of the rally. “No peacefulness after today.”

Islamic militants hold a powerful sway in the lawless and chaotic northern Sinai. They are heavily armed with weapons smuggled from Libya and have links with militants in the neighboring Gaza Strip, run by Hamas. After the attack, Egypt indefinitely closed its border crossing into Gaza, sending 200 Palestinians back into the territory, said Gen. Sami Metwali, director of Rafah passage.

In Cairo, a crowd of tens of thousands of Morsi supporters filled much of a broad boulevard outside a Cairo mosque several blocks away from the Republican Guard headquarters, vowing to remain in place until Morsi is restored. The protesters railed against what they called the return of the regime of autocrat Hosni Mubarak, ousted in early 2011.

“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.”

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.

The Brotherhood has said it will not work with the new military-backed leadership. Morsi supporters say the military has wrecked Egypt’s democracy by carrying out a coup against an elected president. 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 Quran 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-defense” 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.

The night before, the military spokesman issued a statement urging all protesters to remain peaceful. In a message to Morsi’s opponents, Col. Ahmed Mohammed Ali warned against “gloating,” vengeance or attacks on Brotherhood offices, saying there must not be an “endless cycle of revenge.”

The military has a “strong will to ensure national reconciliation, constructive justice and tolerance,” he wrote in an official Facebook posting. He said the army and security forces will not take “any exceptional or arbitrary measures” against any political group.

The first steps for creating a post-Morsi government were taken Thursday, when Mansour, the 67-year-old chief justice of the Supreme Constitutional Court, was sworn in by fellow judges as interim president. A Cabinet of technocrats is to be formed to run the country for an interim period until new elections can be held — though officials have not said how long that will be. In the meantime, the Islamist-written constitution has been suspended.

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.

Mansour also named the head of General Intelligence, Rafaat Shehata, as his security adviser.

Badie and el-Shater were widely believed by the opposition to be the real power in Egypt during Morsi’s term.

The National Salvation Front, the top opposition group during Morsi’s presidency and a key member of the coalition that worked with the military in his removal, has proposed one of its top leaders, Mohammed ElBaradei, as interim prime minister.

That post will hold strong powers since Mansour’s presidency is considered symbolic.

ElBaradei, a Nobel Peace laureate who once headed the U.N. nuclear watchdog agency, is considered Egypt’s top reform advocate.

Also Friday, the African Union suspended Egypt’s membership in the group because of the military’s action against Morsi.

AU Commission head Nkosazana Dlamini-Zuma said in the Ethiopian capital, Addis Ababa, that the removal of Morsi falls under the AU doctrine on unconstitutional changes of government.

The AU usually suspends the membership of countries where the military ousts an elected government.

(AP)