Egypt's election commission said on Saturday that ex-spy chief Omar Suleiman, Muslim Brotherhood candidate Khairat al-Shater and Salafist politician Hazem Abu Ismail are among 10 candidates barred from running for president.
Commission official Tarek Abul Atta told AFP that Suleiman had been disqualified because he failed to get endorsements from 15 provinces as per law.
Shater, who was released from prison in March last year, has been barred because of a law that states that candidates can only run in elections six years after being released or pardoned, Abul Atta said.
Shater had been in jail on charges of terrorism and money laundering during the regime of former president Hosni Mubarak who was forced out of power last year by massive street protests.
Abu Ismail is out of the race because his mother holds another nationality, violating election rules which state that all candidates, their parents and their wives must have only Egyptian citizenship.
Last week an Egyptian court had cleared the way for Abu Ismail to join the race after ruling that his mother was not a US citizen.
Others who have been disqualified include Ayman Nur, who caught the world's attention when he challenged Mubarak in 2005 presidential elections.
Nur was imprisoned shortly after those elections and released on health grounds in 2009. He was banned under the same rule as the Muslim Brotherhood's Shater.
Although the decision was expected by some it threatens to create an upheaval on the political scene, less than six weeks from the election which is due to take place May 23 and 24.
A source close to Suleiman, cited by the state-run MENA news agency, said the former spy chief plans to contest the decision and intends to provide the necessary documents to show that his candidacy is valid.
The Muslim Brotherhood -- which last week announced a second candidate, Mohammed Morsi, in case the first one was disqualified, said it too will appeal appeal the commission's decision, MENA reported.
"This is a political decision," Muslim Brotherhood lawyer Abdelmonein Abdel Maqsud said.
A Brotherhood member, Sobhi Saleh, said on state television: "The legal battle is not over."
Abu Ismail also hit back: "They want to play a game. This is a violation of Egyptian law and the constitution," he told the Islamist television station, Hikma.
Earlier the electoral commission issued a statement saying 10 of the 23 candidates vying for Egypt's top job had been disqualified "because they do not fill one or more of the required conditions." They were not named.
But the disqualified candidates have 48 hours to appeal the decision.
A total of 23 candidates had registered for Egypt's first presidential election since a popular uprising toppled Mubarak last year.
The remaining candidates include former Arab League chief Amr Mussa, who also served as Mubarak's foreign minister for 10 years.
Other candidates still in the race also include former Brotherhood member Abdel Moneim Abul Fotouh and Mubarak's last prime minister, Ahmed Shafiq.
Egypt's Islamist-dominated parliament on Thursday approved a bill that would ban members of Mubarak's regime from standing for public office, but it needs the support of the ruling Supreme Council of the Armed Forces to become law.
Saturday's decision came a day after thousands of Islamists rallied in the streets of Cairo against ex-regime candidates, namely ex-spy chief Suleiman, Mussa -- who also served as foreign minister -- and Shafiq.
Liberal and secular groups also do not wish to see the return of Mubarak-era figures, but they stayed away from Friday's protest.
They have instead called a demonstration on April 20 to denounce what they see as Islamist monopolisation of political life in the country since the revolt.