Egyptian President Abdel Fattah al-Sisi officially launched his bid for a second term in office on Wednesday, submitting documents to register as a candidate, state news agency MENA said, a day after his main potential rival was arrested.

Sisi, who won an election in a landslide in 2014 after leading the army in ousting Muslim Brotherhood's Mohamed Mursi a year earlier, becomes the first candidate to register officially for the election set for March 26-28.

Candidates must register from January 20 to 29 before a final list of candidates is announced on February 20, according to the election commission.

Sisi's popularity has been damaged by austerity reforms, security problems and a crackdown on dissidents, his critics say, but he is widely expected to win the election comfortably.

The electoral commission has said it will ensure the vote is fair and transparent.

Those who have considered challenging Sisi describe a sweeping effort to kill off their campaigns before they begin, with media attacks on candidates, intimidation of supporters, and a nomination process stacked in favour of the former general.

Former military chief of staff Lieutenant General Sami Anan, the last challenger seen as a potential threat to Sisi's re-election, was detained on Tuesday and had his campaign stopped after the army accused him of breaking the law by running for office without permission.

Khaled Ali, a rights lawyer who may be disqualified over a pending court case centred on his alleged use of an obscene hand gesture, remains one of the only presidential hopefuls still actively pursuing a bid.

Ali's campaign said it would hold a news conference on Wednesday to announce their "final position" on the presidential elections.