Tunisians vote Monday on a constitution seen as a referendum on President Kais Saied, whose charter would give his office nearly unchecked powers.
Voting runs from 6:00 am (0500 GMT) to 10:00 pm at some 11,000 polling stations across the North African country.
Around 9.3 million out of Tunisia's 12 million people -- civilians aged over 18 -- have opted in or been automatically registered to vote, according to the ISIE electoral commission.
They include about 356,000 registered overseas, for whom polling began on Saturday, AFP reported.
The referendum comes a year to the day after Saied sacked the government and froze parliament in a dramatic power grab, as Tunisia grappled with surging coronavirus cases on top of political and economic crises.
Many Tunisians welcomed his moves against political parties and the often-deadlocked parliament, part of a system long praised as the only democracy to have emerged from the 2011 Arab uprisings.
No quorum has been set, nor any provision made for a "no" result, and Saied's constitution for a "new republic" is widely expected to pass.
Opposition parties and civil society groups have called for a boycott, while the powerful UGTT trades union has not taken an official stand on the vote.
Saied's charter would replace the country's 2014 constitution.
His supporters blame the hybrid parliamentary-presidential system it introduced, and the dominant Islamist-influenced Ennahdha party, for years of political crises and widespread corruption.
Saied's draft was published earlier this month. The new text would place the head of state in supreme command of the army, give him full executive control and allow him to appoint a government without the approval of parliament.
He could also present draft laws to parliament, which would be obliged to give them priority.
He would be almost impossible to remove from office before the end of his five-year term in 2024.
Saied, a 64-year-old law professor, won a landslide victory in 2019 presidential elections, building on his image as incorruptible and removed from the political elite.
He has vowed to protect Tunisians' liberties and describes his political project as a "correction" and a return to the path of the revolution.
"Lots of young people, the marginalized and excluded, are on his side," said political analyst Hamadi Redissi.