The highest turnout in the 15 October referendum was recorded in the northern Kurdish province of Arbil, at 90%. The lowest was in the Sunni Arab province of al-Anbar, a hotbed of Iraq's 30-month-old anti-US violence, at 32%.
But Sunni Arabs participated in much larger numbers than in January, when most of them boycotted the vote. Only 2% of al-Anbar's registered voters cast ballots in January.
Another Sunni Arab majority province, Salah al-Din in central Iraq, saw the second highest turnout last weekend, with 88%, said Farid Ayar, a senior member of the Independent Electoral Commission of Iraq, on Friday.
Salah al-Din includes Saddam Hussein's hometown of Tikrit and the anti-US strongholds of Samarra, Balad and Baiji.
Al-Anbar, which stretches for hundreds of miles west and northwest of Baghdad, includes other anti-US bastions such as Ramadi, al-Qaim and Haditha.
Turnout in Baghdad, a city of an estimated six million people, was 56%, said Ayar.
The official results of the vote
are expected next week
Across the country, 9,775,000 people cast ballots.
The official results of Saturday's referendum are expected to be announced next week, a delay caused by the need to audit results from several provinces that commission officials said showed an unexpectedly high number of yes votes.
Initial figures leaked by electoral officials suggested the yes vote won in 16 of Iraq's 18 provinces, with a vast majority in Salah al-Din and al-Anbar voting no.
That would mean the constitution's passage, but it is not known how the audit will affect the final figures.
Turnout for January's vote was estimated at about 60%.
Iraqis will return to the polls on 15 December in a general election to be held regardless of the result of Saturday's referendum.
If the charter is adopted, the December election will produce a full-term parliament.
If it is rejected, the vote will be for another interim chamber that will attempt again to draft a constitution.