Egyptian officials are urging voters to turn out in high numbers for a three-day referendum on extending President el-Sissi's rule.
Prime Minister Mustafa Madbouly cast his ballot on Saturday. He says that voting will reflect "the atmosphere of stability and democracy that we are witnessing now."
Heavy police and army security was reported at polling stations throughout the capital city.
Egyptians have begun voting on constitutional amendments aimed at keeping President el-Sissi in power until 2030.
The referendum comes amid an unprecedented crackdown on dissent in recent years. El-Sissi's government has arrested thousands of people, most of them Islamists but also prominent secular activists, and rolled back freedoms won in a 2011 pro-democracy uprising.
The proposed changes were blasted by critics as another major step toward authoritarian rule.
Egyptians are being asked to vote on constitutional amendments that would allow President Abdel-Fattah el-Sissi to stay in power until 2030.
The three-day voting period for the nationwide referendum starts at 9 a.m. (0700 GMT) Saturday on proposed changes that would also further enshrine the military's role in politics. Parliament, packed with el-Sissi supporters, overwhelmingly approved the amendments on Tuesday.
Opposition parties have called on voters to reject the changes, seen by critics as a step backward to authoritarianism eight years after a pro-democracy uprising.
The vote comes amid an unprecedented crackdown by authorities on dissent since the military ouster of an elected but divisive president in 2013.
El-Sissi came to power in 2014 and was re-elected for a second four-year term last year.
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