The referendum saw just 27.5 percent of 9.3 million registered voters cast ballots, with an overwhelming 92-93 percent supporting the new constitution.
Tunisian President Kais Saied's supporters have celebrated the almost certain victory of the "yes" vote in a referendum on a new constitution that strengthens the powers of the head of state.
"Tunisia has entered a new phase," Saied said on Tuesday, appearing in front of a jubilant crowd at around 0100 GMT.
According to local television, he added that "there was a large crowd in the polling stations and the rate would have been higher if the vote took place over two days".
The referendum, held a year to the day after Saied sacked the government and froze parliament in what rivals have called a coup, saw at least 27.5 percent of 9.3 million registered voters cast ballots, Tunisia's ISIE electoral commission said late Monday.
An overwhelming 92-93 percent of those who voted supported the new constitution, according to an exit poll taken by the Sigma Conseil institute. Initial results are due Tuesday afternoon.
After the projected outcome was announced on national television, Saied's supporters drove cars in procession through central Tunis.
They waved flags and beeped their car horns, with some singing the national anthem or shouting slogans supporting the president.
Election law in focus
Saied said the first decision after the constitutional referendum would be to draft an election law. He added that the law will change the format of the old elections wherein elected officials did not reflect the will of the voters.
Saied's move against a system that emerged after the 2011 overthrow of strongman Zine el Abidine Ben Ali was welcomed by a section of Tunisians fed up with high inflation and unemployment, political turmoil and a system they felt had brought little improvement to their lives.
But Saied's critics have warned the new constitution would lock in presidential powers that could dismantle the democratic gains of the 2011 revolution by handing him nearly total power.
The new text would place the president in command of the army, allow him to appoint a government without parliamentary approval and make him virtually impossible to remove from office.
He could also present draft laws to parliament, which would be obliged to give them priority.