Egyptian President Abdel Fattah al-Sisi has been re-elected for a second term with 92 per cent of the vote, state media reported on Thursday citing preliminary results.

Some 23 million of the 60 million registered voters turned out during the three days of polling that ended Wednesday, state-owned newspapers Al-Ahram and Akhbar el-Youm, and the official Mena news agency reported.

According to Al-Ahram, in addition to the 23 million who cast valid votes, two million spoiled their ballot papers, inserting the names of candidates who were not among the only two approved.

President Sisi's sole challenger was the little-known Moussa Mostafa Moussa, himself a supporter of the president, who registered immediately before the close date for applications, saving the election from being a one-horse race.

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

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President Sisi, who ousted Egypt's first freely elected president — Islamist Mohamed Morsy — after mass street protests in 2013, won his first term in 2014 with 96.9 per cent of the vote.

Turnout of 47 per cent in that year's election was sharply higher than this year's 40 per cent despite appeals from President Sisi 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, the electoral commission has warned.