Authorities have been urging Egyptians to participate in the three-day vote, hoping for a high turnout despite what is seen as a foregone conclusion.

Sisi's sole rival is Moussa Mostafa Moussa -- himself a supporter of the president.

Other candidates withdrew, were sidelined or detained.

Sisi, a former army chief elected in 2014 a year after ousting his Islamist predecessor Mohamed Morsi, urged voters to turn out en masse.

The army had ousted Morsi following mass protests against the divisive Islamist, and Sisi remains popular, but tough economic reforms that ratcheted up inflation appear to have dented his popularity.