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.