CAIRO—Egypt´s Presidential Elections Commission will exclude 10 candidates, including three prominent frontrunners, from presidential elections next month, a decision that is likely to stoke popular outrage across Egypt´s political spectrum.

Farouq Sultan, a judge and the head of the commission, said Saturday night that Muslim Brotherhood candidate Khairat Al Shater, former intelligence chief Omar Suleiman and hardline Islamist preacher Hazem Abu Ismail will be barred from running.

Mr. Sultan gave no explanation for the candidates´ exclusion. The ten presidential hopefuls will have 48 hours to appeal the decision.

If the excluded presidential candidates fail in their appeals, the popular backlash is likely to be overwhelming.

The announcement threatens to launch a renewed round of instability only a month before Egypt´s first post-revolutionary presidential elections and little more than two months before the military has promised to hand over power to an elected civilian president.

"This is a purely political decision," said Mourad Mohamed Ali, the head of Mr. Shater´s presidential campaign. Mr. Ali said the decision was directed by Egypt´s interim military leadership who he said were working to undermine Egypt´s revolution and reconstitute the ousted regime of former President Hosni Mubarak.

"It´s not about whether Shater will be able to go for the election or not. We are talking about human rights. We are talking about legitimacy. We are talking about the direction of Egypt," he said.

Yet Mr. Suleiman´s exclusion, alongside hardline Islamists such as Mr. Shater and Mr. Abu Ismail, complicates perceived notions that the election commission´s decision was a purely political gesture aimed at checking the rise of Islamist politicians.

Since Mr. Suleiman announced his participation in the race last week, furious Islamist and liberal activists alike have maligned him as an extension of the military regime. The rumors became so pervasive that the normally tight-lipped intelligence services announced on Saturday that they were not supporting or campaigning on Mr. Suleiman´s behalf.

The presidential elections commission said Mr. Suleiman was disqualified because he failed to gather supporters´ signatures from at least 15 different governorates in accordance with campaign laws.

Mr. Ali speculated that the commission may have excluded Mr. Suleiman as a token gesture of fairness to justify sidelining Islamist candidates. The Brotherhood has "indicators" that the nominally independent election commission is operating under orders from the ruling Supreme Council of the Armed Forces, or SCAF.

The SCAF appointed judges who populate the election commission. The generals will meet with the heads of egyptian political parties to discuss the announcement, according to egypt´s official state media agency.

If the commission´s decisions are upheld, the presidential field will be clear for Amr Moussa, the popular former secretary general of the Arab League, to dominate the vote. Mr. Moussa, who also served as Mr. Mubarak´s minister of foreign affairs, has spent the past year leading the presidential pack, according to poll figures.

Campaign staff for Mr. Suleiman, Mr. Shater and Mr. Abu Ismail said they planned to appeal the decision. But supporters for both candidates have demonstrated a willingness to take to the streets in defense of their candidates.

Thousands of mostly Islamist demonstrators filled Cairo´s Tahrir Square on Friday to demand that the military leadership approve a law excluding Mr. Suleiman from the race because of his connections to the ousted regime of Hosni Mubarak.

Sharing the same space and many of the same chants were thousands of supporters of Mr. Abu Ismail. Mr. Abu Ismail´s candidacy has been under threat for weeks since revelations surfaced that his late mother held American citizenship.

Under a constitutional declaration passed by the military last March, the children of foreign nationals are ineligible to run for president.

Supporters of Mr. Abu Ismail, a lawyer-turned-preacher, have developed a reputation for extreme devotion.

Egypt´s military was deployed Friday night to protect the offices of the presidential election commission after hundreds of Mr. Abu Ismail´s fans— known has "Hazemoon" after the candidate´s first name— surrounded the building to demand that their candidate be included in the voter rolls.

Mr. Ali said the election commission excluded Mr. Shater because of a 2006 sentence to seven years in prison on charges of money laundering. The SCAF released Mr. Shater last year and pardoned him late last month, several days before the Brotherhood announced his candidacy.

Mr. Ali said the legal standing of Mr. Shater´s candidacy was "very solid."

In anticipation of Mr. Shater´s possible exclusion, the Brotherhood nominated Mohamed Morsi, the chairman of the Brotherhood-backed Freedom and Justice Party, as their second candidate for president last week.

The reasoning behind Mr. Suleiman´s exclusion was less clear. Egypt´s Islamist-dominated parliament passed legislation aimed at blocking the candidacies of Mr. Suleiman and Ahmed Shafiq, Mr. Mubarak´s final prime ministerial appointee before his ouster last February. The military leadership, however, has not approved the legislation and legal experts have said courts will probably deam the bill unconstitutional. (Copyright © Dow Jones & Company, Inc.) 04/15/12)