Former military chief Abdul Fattah al-Sisi is heading for a huge victory in Egypt's presidential election, preliminary results have shown.

He had gained about 90% of the vote after 2,000 of 12,000 polling stations reported their results.

However, turnout is expected to be lower than 45% despite a massive push to get more people to polling stations. Many groups boycotted the vote.

Retired field marshal Mr Sisi overthrew President Mohammed Morsi last July.

He has overseen a bloody purge of Mr Morsi's Muslim Brotherhood movement in which more than 1,400 people have been killed and 16,000 detained.

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The Brotherhood said it would boycott the vote, as did many liberal and secular activist groups.

Hamdeen Sabahi, the only other candidate in the election, said earlier his team had recorded "violations" in the voting process.

However, he rejected calls from his supporters to withdraw from the elections, saying it was not in the interest of Egyptians.

The military-backed authorities had extended voting to a third day in the hope of boosting turnout.

But reports suggested many polling stations were almost deserted on Wednesday.

Analysts say the low turnout damages Mr Sisi's authority before he takes office.

He had aimed to get 40 million of 54 million registered voters to the polling stations, to show that he had the support of the majority of Egypt.

In the event, it appears fewer than 25 million voted.

In comparison, turnout for the previous presidential election between Mohamed Morsi and former Prime Minister Ahmed Shafiq was around 52%.