Egyptian voters have overwhelmingly backed constitutional changes that could see President Abdel Fattah Al Sisi's rule extended to 2030, the electoral board said on Tuesday.

National Election Authority head Lashin Ibrahim told a Cairo press conference that 88.83 per cent voted "yes" in a referendum on the amendments, with 11.17 per cent voting "no".

The three-day vote took place "in a democratic climate powered by freedom," he added.

A man walks in front of a banner reading, "Yes to the constitutional amendments, for a better future," in Cairo. File/Reuters

Sisi took to Twitter shortly after the results were announced to thank his fellow citizens "who dazzled the world with their awareness of the challenges facing" Egypt.

Around 27 million votes were cast in the Arab world's most populous country, with a turnout rate of 44.33 per cent.

Other controversial amendments include boosting Sisi's control over the judiciary and giving the military even greater influence in Egyptian political life.

No one near 'throne'

Sisi has argued he needs longer to complete the job of restoring security and stability after the turmoil that followed the overthrow of veteran autocrat Hosni Mubarak in the Arab Spring of 2011.

A vote in Sisi's favour was expected but analysts worried about its consequences.

The main amendment, which has set the nation abuzz, is the near certainty that Sisi will run for another six years in office when his term ends in 2024.

His current term was to end in 2022 but was retroactively updated with an extra two years.

Riding a populist wave after militarily overthrowing president Mohamed Morsi in July 2013, Sisi cruised to a presidential victory in 2014 and was re-elected with more than 97 per cent of the vote in 2018.

Agence France-Presse