CAIRO -- Islamist and revolutionary groups packed Tahrir Square on Tuesday in protest of constitutional changes by Egypt's military government, presenting the generals with their first major challenge in the streets following the weekend's presidential election.

Spokesmen for the campaign of Mohamed Morsi, the Muslim Brotherhood candidate and apparent winner of the election, claimed earlier in the day that the coalition would "stage a million man march." While numbers fell well short of that goal as well as the crowds seen during the 2011 revolution, the march brought out the tens of thousands who had been missing during the run-up to the elections.

Tuesday's demonstration, which brought the Muslim Brotherhood and more conservative Salafis together with revolutionary groups and liberal parties, was an attempt to pressure the Supreme Council of the Armed Forces, Egpyt's military ruler, to withdraw changes to the constitution.

The military's constitutional announcement, issued within minutes of the end of voting on Sunday, gave many of the key powers of the presidency to the armed forces, including the right to draft laws and name a new panel to create Egypt's permanent constitution. A SCAF spokesman reiterated earlier in the day that the former panel, appointed by the now-dissolved Parliament, would have a week to complete its work before being replaced.

"We are not coming today for a celebration," said Rami Said, a member of the April 6th Youth Movement, one of the leading revolutionary groups. "We are coming to limit SCAF and to say enough to them." Many in the crowd, including several members of Parliament from the Muslim Brotherhood-affiliated Freedom and Justice Party, stressed this goal in interviews with The Huffington Post.

"We're here to refuse the extraordinary measures" of the military, said Nazar Nabit, an Freedom and Justice Party legislator, calling the military's moves "illegal and immoral."

Despite the political aim of the rally, the crowd was in a celebratory mood. Fireworks exploded over the square and groups of men paraded under large banners or roamed Tahrir on the back of flatbed trucks, waving flags and chanting pro-Morsi slogans. With few police officers or soldiers visible, the crowd lacked fear or tension.

"I'm sure the fear barrier is broken," said Ayman Helmi, who proved his own point by arriving from Sadat City, about 100 kilometers from Cairo, with his young son Ahmed. "The Egyptian people will not stand down."

The party atmosphere rose to new heights when rumors of the death of former President Hosni Mubarak reached the square at around 11 p.m. But while the state news agency claimed that Mubarak was "clinically dead" -- a condition whose meaning was never fully clarified -- conflicting reports flooded the airwaves and Internet. SCAF later said that Mubarak had not in fact died.

The Muslim Brotherhood was eager to show political unity against the military, touting the participation of other groups and even praising the April 6th revolutionaries from the stage set up beside the square. But the crowd seemed overwhelmingly drawn from the Brotherhood's ranks, which filled the center of Tahrir while revolutionaries gathered at the edges. Some of the loudest chants were those of Morsi's name and the boast that "Morsi is the president of the republic."

There were also signs of new fault lines that have emerged since the revolution. Then, protesters chanted, "The people, the army, one hand," to appeal to soldiers for protection against police and thugs controlled by then-President Mubarak. But after nearly a year and a half of military rule, the first part of the phrase was dropped as the crowd roared the slogan, recast as a call for political unity against military rule.

"People have to go back to the square in peaceful demonstrations to have all of our demands and to group all of the political forces in one hand to accomplish these matters," said Nabit, the legislator.

The constitutional declaration was just one of several attempts by SCAF to secure the military's interests as the elections played out. Last week, the constitutional court dissolved Parliament just two days before the election, removing the Muslim Brotherhood's power base within the government. The military has also been given wide powers to arrest civilians, which many Egyptians saw as a de facto return to the emergency law in effect for decades.

The Morsi campaign and revolutionary groups that include the April 6th Youth Movement, which backed Morsi in the election, have deemed all of those actions illegitimate, refusing to acknowledge even the possibility that they will succeed.

The march capped a day in which the Muslim Brotherhood and the Morsi campaign challenged to military's authority. In a morning press conference at Morsi's media headquarters, his campaign announced full results from the election, claiming that Morsi had won with 52 percent of the vote. While the results are still unofficial, the Morsi campaign employed an army of poll watchers and said their numbers were the same ones given to election officials. The Shafik campaign disputes Morsi's figures.

"The most professional campaign and the most accurate campaign has always been the Muslim Brotherhood," said Abdel Rahman Yusuf, who was the campaign coordinator for eliminated candidate Adbel Moneim Aboul Fotouh. "It's hard to believe that they counted a million votes by mistake."

Morsi's spokesmen also swiped at the military's constitutional declaration, which contains the threat of a neutered presidency. Morsi, they said, "will be a president with full authorities."

Amr Ali, an April 6th representative, said marches will continue daily until the military withdraws the constitutional declaration. And if Ahmed Shafik should be announced as the winner of the election later this week, another demonstrator had a ready answer: "We are not afraid of blood."

Loading Slideshow...
  • An Egyptian woman chants anti-Supreme Council for the Armed Forces (SCAF) slogans outside the Egyptian Parliament in Cairo, Egypt, Tuesday, June 19, 2012. The campaign of an Islamist who claimed victory in Egypt's presidential runoff says the Muslim Brotherhood and other political groups plan a mass demonstration later Tuesday to protest a military declaration seeking to curtail the powers of the next president. (AP Photo/Manu Brabo)

  • Egyptians argue during a protest near the Egyptian Parliament in Cairo, Egypt, Tuesday, June 19, 2012. The campaign of an Islamist who claimed victory in Egypt's presidential runoff says the Muslim Brotherhood and other political groups planned a mass demonstration later Tuesday to protest a military declaration seeking to curtail the powers of the next president. (AP Photo/Manu Brabo)

  • Anti-Riot soliders sit behind a closed gate barring entry to the Egyptian Parliament in Cairo, Egypt, Tuesday, June 19, 2012. (AP Photo/Manu Brabo)

  • Egyptian activists shout slogans against military rule in front of the parliament compound in Cairo, Egypt, Tuesday, June 19, 2012. (AP Photo/Amr Nabil)

  • Anti-riot soldiers sit behind a closed gate barring entry to the Egyptian Parliament in Cairo, Egypt, Tuesday, June 19, 2012. Egypt's highest court has ordered the country's Islamist-dominated parliament dissolved, saying its election about six months ago was unconstitutional. (AP Photo/Amr Nabil)

  • A family supporting Egyptian presidential candidate Mohammed Morsi flash the "V" sign during celebrations of their candidate's claimed victory, in Tahrir, Square, Cairo, Egypt Monday, June 18, 2012. (AP Photo/Nasser Nasser)

  • Supporters of Egyptian presidential candidate Mohammed Morsi chant slogans and wave national flags during celebrations of their candidate's claimed victory, in Tahrir Square, Cairo, Egypt Monday, June 18, 2012. (AP Photo/Nasser Nasser)

  • Supporters of Egyptian presidential candidate Mohammed Morsi gather around two motorcyclists spinning a rickshaw and a motorcycle during celebrations of their candidate's claimed victory, in Tahrir Square, Cairo, Egypt Monday, June 18, 2012. (AP Photo/Nasser Nasser)

  • An Egyptian vendor displays pins of Muslim brotherhood candidate Mohammed Morsi and Arabic that reads, "revival" in Tahrir Square, Cairo, Egypt, June 18, 2012. (AP Photo/Amr Nabil)

  • Egyptian supporters of Muslim brotherhood candidate Mohammed Morsi celebrate in Tahrir Square, Cairo, Egypt, June 18, 2012. (AP Photo/Amr Nabil)

  • Egyptian supporters of Muslim brotherhood candidate Mohammed Morsi hold a poster with Arabic that reads, "'Mohammed Morsi, president for Egypt" in Tahrir Square, Cairo, Egypt, June 18, 2012. (AP Photo/Amr Nabil)

  • An Egyptian man holds the Quran as he celebrates Islamist candidate Mohammed Morsi's apparent victory in Tahrir Square, Cairo, Monday, June 18, 2012. (AP Photo/Manu Brabo)

  • Egyptian supporters of Muslim brotherhood candidate Mohammed Morsi celebrate his apparent victory as they hold flowers in Tahrir Square, Cairo, Monday, June 18, 2012. (AP Photo/Amr Nabil)