Egyptians have begun three days of voting to elect a new president, in an election expected to produce a landslide for the incumbent.

There are few doubts that President Abdul Fattah al-Sisi will win a second term after most challengers withdrew.

The only other candidate is the little-known centrist politician Moussa Mostafa Moussa.

But Mr Moussa is known to be a supporter of the president, and has said he supports Mr Sisi's re-election.

Egypt, which has a population of 84 million, is the largest Arab country and has played a central role in Middle Eastern politics in modern times.

Why are there only two candidates?

Seven candidates initially put themselves forward for the presidency but the majority of them pulled out of the race, including human rights lawyer Khalid Ali and former Prime Minister Ahmad Shafiq.

A former chief of staff in the Egyptian army, Sami Anan, was detained in January after announcing his intention to run.

He was widely considered to be the last high-profile challenger to the president.

It led some opposition figures to call for a boycott of the vote, but Mr Sisi's campaign spokesman said no candidates had been prevented from running.

The authorities have been encouraging voter participation and buses with loudspeakers drove through the capital Cairo playing songs urging people to turn out and vote.

What are the key issues?

Mr Sisi has been in power since 2013, when he led the overthrow of Islamist President Mohammed Morsi following mass protests against his rule. He then won a landslide in the 2014 presidential election.

His supporters say his first term has brought stability to a country that has been rocked by unrest since 2011.

Egypt has witnessed the overthrow of two presidents since that year's Arab Spring protests.

But some critics have pointed to the controversial build-up to the vote and the lack of opposition.

It is expected that Mr Sisi will win a second term comfortably but turnout figures are the main focus for many due to the calls for an opposition boycott.

Has there been unrest?

Ahead of the vote, the Egyptian interior ministry said police had killed six militants suspected of being behind a failed attempt to assassinate a security chief.

General Mostafa al-Nemr escaped unhurt when a bomb that was left under a car in Alexandria exploded as he drove past. Two police officers were killed in the attack.

In a statement, the ministry said it had tracked down a cell belonging to the Hasm movement and the militants were killed during an exchange of fire.