Egyptian president Abdel Fatah al-Sisi has been re-elected for a second term after an election campaign in which five of his potential challengers were prevented from getting on the ballot.

Preliminary results showed that Sisi won about 92% of the vote, with turnout at around 41.5%.

Twenty-five million of the 60 million registered voters turned out during the three days of polling that ended on Wednesday, state-owned newspaper Al-Ahram reported. Twenty-three million voted for Sisi.

The Akhbar el-Youm newspaper did not report the full turnout but said Sisi won 21.4 million votes.

Abdel Fatah al-Sisi, who was re-elected with about 92% of the vote.

According to the Al-Ahram newspaper, in addition to 23 million who cast valid votes, 2 million spoiled their ballot papers.

Sisi’s sole challenger was Mousa Mostafa Mousa, who previously declared that he “was not here to challenge the president” and who entered the race at the last minute after five other potential challengers were blocked from getting on the ballot.

Mousa conceded his loss on Wednesday night, telling a TV station he had hoped for 10% of the vote. “But I know the immense popularity of President Sisi,” he said.

Other, more heavyweight would-be challengers were all sidelined, detained or pulled out.

As army chief, Sisi ousted Egypt’s first freely elected president, Islamist Mohamed Morsi, after mass street protests in 2013, then went on to win his first term in 2014 with 96.9% of the vote.

Timeline After Tahrir Square Show Egyptian president Hosni Mubarak steps down after almost 30 years in power amid anti-government Arab spring protests. Rallies continue all year. Islamist parties win drawn-out parliamentary elections. Mohamed Morsi of Muslim Brotherhood wins presidential election. Mubarak sentenced to life in prison for complicity in killing 800 protesters in 2011. Army overthrows Morsi. Security forces kill hundreds in pro-Morsi camp. Former army chief Abdel Fatah al-Sisi wins presidential election. Morsi sentenced to death. Egypt's appeal court orders retrial in 2016. Isis claims responsibility for bombing Russian plane in Sinai. Crew and 224 tourists killed. IMF approves three-year $12bn loan to Egypt designed to help country out of economic crisis. Suicide bombers kill dozens at two churches as worshippers celebrate Palm Sunday. Egyptian airstrikes on northern Sinai after militants assault on a mosque kills 305 people. Sisi announces he will run for a second term. Sisi wins snap Egyptian referendum amid vote-buying claims. It could keep him in power until 2030. Mohamed Morsi, ousted president of Egypt, dies in court. Hosni Mubarak dies at 91.

Turnout of 47% in that year’s election was higher than this year’s 40% despite appeals from Sherif Ismail, the prime minister, for voters to fulfil their patriotic duty.

Boycotters who cannot show good reason for not going to the polls could a face a fine of up to 500 Egyptian pounds (£20), the electoral commission has warned.

At a news conference, election commission official Mahmud al-Sherif said there had been no violations of Egypt’s election law.

Opposition groups had called for a boycott of this week’s vote, which they labelled a facade. There were no presidential debates and Sisi himself did not appear at any official campaign events, although he spoke at a number of ceremonies.

In an interview days ahead of the vote, Sisi said he had wished there were more candidates, denying any role in sidelining them.

At a speech before the vote, he also called for a high turnout. “I need you because the journey is not over,” Sisi told a mostly female audience. “I need every lady and mother and sister, please, I need the entire world to see us in the street voting.”

Morsi’s removal had ushered in a deadly crackdown that killed and jailed hundreds of Islamists. The initial attack on Morsi’s supporters expanded to include liberal and leftist secular activists.