Leftist candidate Hamdeen Sabahi will appeal for Egypt's presidential election to be suspended over alleged voting irregularities and a pending case over one of the front-runner's right to stand, Sabahi's lawyer has said.
Sabahi's pledge to pursue a suspension came on Saturday as the two apparent winners of the first round reached out to rival candidates ahead of a June run-off that appears set to polarise the country.
Final votes were still being counted, but unofficial results suggested that the top two front-runners out of 12 candidates were the Muslim Brotherhood's Mohammed Morsi and Ahmed Shafiq, a former prime minister under Hosni Mubarak.
International monitors have described the initial voting process as "encouraging", in advance of the release of official results by Tuesday.
On Friday night, the Brotherhood said it was seeking to create a coalition of forces to challenge Shafiq, reaching out to Morsi's former rivals, including Abdel Moneim Aboul Fotouh, who left the organisation before running for president.
According to Egyptian state television, preliminary results showed Sabahi in third place behind Shafiq and Morsi after this week's first round. Only the top two go through to a runoff on June 16 and 17.
"We will present an appeal on behalf of candidate Hamdeen Sabahi ... to the presidential electoral committee, citing a series of irregularities ... that have affected the outcome of the first round," lawyer Essam El-Islamboly told the Reuters news agency.
Islamboly said the appeal, to be lodged on Sunday or Monday at the latest, would ask the electoral committee to suspend the election until the prosecutor-general had checked a claim by a police officer that the interior ministry had illegally assigned 900,000 votes to Shafiq.
He said Sabahi also wanted the election halted until the constitutional court rules on the validity of an April decision
by the electoral committee to disqualify Shafiq.
The committee swiftly lifted its ban on Shafiq, but referred a new law barring top Mubarak-era officials from the race to the constitutional court.
Shafiq, who placed second, says votes cast for him in one province were not included.
Sabahi's appeal to the commission demands a partial vote recount, after he placed third by a margin of 700,000 votes.
Aboul Foutoh, who finished fourth, filed an appeal on Saturday. His lawyer says he has proof that votes were cast on behalf of dead people.
"Sunday is the last day for candidates to file any complaints," Al Jazeera's Rawya Rageh reported from Cairo.
"All candidates had the right to have representatives at polling stations during the election to act as monitors and observe the process and then come back with violations perceived during the vote," our correspondent said.
The choice between Morsi and Shafiq, representing forces that have wrestled for the past six decades, has dismayed many Egyptians who voted for candidates offering a middle ground.
They fear a victory for the 70-year-old Shafiq would end hopes for change ignited by last year's uprising, while a win for Morsi would pitch Egypt into the uncertainties of experimenting with Islamic rule.
In an attempt to broaden support, the Brotherhood's candidate met public figures and political groups on Saturday. But three of the invited presidential candidates, including Sabahi, did not show up.
Speaking after the meeting, Morsi said that his group respected democratic principles, and said that his candidacy was the only way to ensure that Mubarak's regime was not recreated by Shafiq.
"We are certain that the remnants of Mubarak's regime and his gang, and those that belong to it... will fall flat and will land in the rubbish bin of history,'' he said.
The Brotherhood already holds the biggest bloc in parliament after elections completed in January, but has been unable to assert itself against an army-appointed interim government.
Shafiq used similar language at a news conference in which he addressed youth groups that spearheaded last year's revolt. For many voters, however, he represented everything they wanted changed.
"Your revolution has been hijacked and I am committed to bringing [it] back," he told the youth that led the popular uprising in 2011, in an apparent reference to the Muslim Brotherhood, which already controls parliament.
He urged unity for those "who dream and those who are angry, the ambitious and the despondent, the unemployed and the employed, the Muslims, the Copts, the Islamists, the liberals and the leftists".
"Let's build and not seek revenge," he told a news conference.
Much of his rhetoric indirectly targeted the Brotherhood, playing on fears among Egypt's minority Christians and secular
liberals that a Morsi presidency would threaten their freedoms.
On Friday, he told Egyptian television he saw no problem with the idea of a Muslim Brotherhood-led government if he were elected president.
The generals who took over when Mubarak quit in February 2011 have promised to make way for a new president by July 1, formally ending a messy and often bloody political transition.
But the military, the source of all Egypt's past presidents, is keen to keep its privileges and influence, preferably enshrined in a new constitution.
Political wrangling has held up the drafting process, so the next president will take office not knowing his powers or those of parliament and government.
Shafiq was appointed prime minister during Mubarak's last days in power in a bid to appease the popular revolt that eventually overthrew the longtime leader.
But he has been criticised for his association with the old regime and for having retained many Mubarak ministers in his cabinet, a decision that later forced him to resign under pressure from youth movements that spearheaded the uprising.
Although Morsi finished first in the presidential poll, his share of the vote was unimpressive compared to the Brotherhood's performance in the parliamentary election in which it gained nearly half the seats.