A voter casts her ballot on constitutional amendments at a polling station in Cairo. Egyptians are voting on constitutional amendments that would allow President Abdel-Fattah el-Sissi to stay in power until 2030. Picture: Amr Nabil/AP

Cairo - Egyptians were voting on Monday, the third and final day of a referendum on contested constitutional amendments that could allow President Abdel-Fattah al-Sissi to rule until 2030.

Pro-government media and political parties have intensified calls on voters to go to polls, which opened for the day at 9 am (0700 GMT).

Footage on local television stations showed voters queuing at polling stations in several parts of Egypt during the first three hours of the balloting.

Some voters called on their compatriots to go to polls in large numbers, in a vote that has largely been seen as a test of popular support for al-Sissi.

"Come and participate so that your country will progress," a female voter said in remarks to state television, addressing absentee voters.

"Your votes will boost Egypt's democratic image in front of the world," the woman added at a polling station in the Nile Delta province of Kafr al-Sheikh.

Other voters flashed the victory sign and waved the Egyptian flag as they waited to cast their ballots.

In the province of Mansura, some 110 kilometres north of Cairo, women let out traditional joy cries, as others danced outside a polling station there.

Vehicles with loudspeakers broadcasting patriotic songs were roaming Cairo streets telling potential voters to "do the right thing" and cast their ballots.

On the first two days of the plebiscite, voters in some poor areas in the capital were offered packets of food staples distributed by government loyalists in order to boost turnout, according to witnesses.

Free transportation to the polling stations was also reported. Sponsors said the gesture was aimed at encouraging voters to go to the polls.

A commission in charge of the referendum said it would refer any electoral violation such as influencing or bribing voters to prosecutors.

The commission also said it had cancelled a one-hour break in balloting in order to ease "crowding" at the polls.

Voting runs nationwide until 9 pm.

Al-Sissi took office in 2014, a year after the then-army general led the overthrow of Mohammed Morsi, the country's first democratically elected but divisive president who was a senior figure in the Muslim Brotherhood.

The amendments would extend al-Sissi's current second term from four to six years, to end in 2024.

A proposed provisional article would allow him to run for one more six-year term, potentially letting him stay in power until 2030.

The proposed changes to the 2014 constitution also allow the president to appoint senior judicial positions and envisage a bigger role for the army.

The opposition and rights advocates have condemned the amendments as undemocratic.

Proponents of the proposed changes say they are necessary for long-lasting stability in Egypt.

About 61.3 million Egyptians are eligible to vote, according to official figures.

The final result of the referendum is expected to be officially announced by April 27.