Egypt's electoral commission has confirmed that the mother of a self described Islamist candidate holds a US passport, a status that will likely disqualify Hazem Abu Ismail from the country's presidential race.
A commission statement on Saturday said the foreign ministry had confirmed that Abu Ismail's mother, Nawal Abdel Aziz Nur, obtained US citizenship in October 2006.
Egypt's constitution prohibits candidates whose parents hold dual nationality from participating in the poll.
Abu Ismail, a leader of the Salafi party and one of the election frontrunners, has become a familiar sight in Cairo, with his posters adorning many cars and buses.
Thousands of people rallied in central Cairo in support of his candidacy on Friday.
"The people want Hazem Abu Ismail! No to manipulation!" the demonstrators shouted after making their way through central Cairo to Tahrir Square, epicentre of last year's revolt which toppled president Hosni Mubarak.
The protesters carried portraits of Abu Ismail and waved their fists, angrily condemning any attempt to disqualify their candidate.
This came after election commission chief Hatem Degato said on Thursday that the agency had received information according to which Abu Ismail's mother had "used an American passport for travel to and from Egypt" before her death.
Degato told the Reuters news agency that the commission would give a verdict on Abu Ismail's elegibility after this Sunday's deadline for all presidential candidates to submit their applications to run.
Islamists lead race
Files will be examined on April 12-13 and any candidate not meeting the requirements will be informed, the commission said.
Those rejected would then have 48 hours to appeal before the final list of candidates is announced on April 26.
Abu Ismail launched his candidacy on March 30 with a large motorcade that took him to the electoral commission headquarters in Cairo.
He advocates a strict interpretation of Islam similar to the one practised in Saudi Arabia
He would compete with more moderate Islamist candidates such as senior Muslim Brotherhood figure Khairat El-Shater and former regime figures such as former foreign minister Amr Moussa.
Meanwhile, an administrative court in Cairo on Saturday banned another candidate, Ayman Nour, from running in the presidential elections, Egypt's state news agency reported.
The ruling relates to a previous sentence under Mubarak, which gave him five years in prison for forging documents to licence his political party el-Ghad. He says the case was politically motivated.
Also on Saturday, the Gamaa Islamiya, an ultraconservative Islamist party, put forward prominent imam Safwat Hegazy as its presidential candidate. Hegazy was recently banned from entering France along with a number of other high-profile Muslim clerics on the grounds that they "call for hatred and violence".
Elsewhere, Omar Suleiman, the former intelligence chief under Mubarak, said on Friday that he had also decided to run in the election, two days after he ruled himself out of the race.
His change of mind came after a group of demonstrators gathered to urge Suleiman to run, said a statement attributed to him.
Overall, Islamists have made big political strides since Mubarak's ousting, winning majorities in elections to both houses of parliament.
The Muslim Brotherhood's Freedom and Justice Party won the most seats in parliamentary elections earlier this year, with the Salafists capturing nearly a quarter of the seats.