Egypt's state news agency says expats have started voting on constitutional amendments that would allow President Abdel-Fattah el-Sissi to stay in power until 2030.

MENA reported that Egyptians living abroad lined up outside their country's diplomatic missions to vote on Friday, a day before the referendum starts in Egypt. The voting is to last three days, to maximize turnout.

The changes to the constitution are seen by critics as another step back toward authoritarianism, eight years after a pro-democracy uprising ended Hosni Mubarak's 30-year rule and nearly six years after el-Sissi led a popular military overthrow of the country's first freely elected but divisive Islamist president, Mohammed Morsi.

Since el-Sissi took office, his government has overseen an unprecedented crackdown on dissent.

The opposition has urged Egyptians to vote "No."