Polls across Egypt closed on Wednesday evening after a second and final day of voting on a draft constitution that could pave the way for a presidential bid by army chief General "Abdel Fattah al-Sisi".
Voting passed off more peacefully than on Tuesday, when nine people were killed, but officials said police arrested at least 79 people on Wednesday during protests by supporters of deposed President "Mohamed Mursi", removed from power by Sisi in July.
State media reported that polls had closed, counting had begun, and unofficial results could filter out within hours.
The constitution was expected to be approved easily. There has been little sign of opposition to it following a fierce government crackdown on Mursi's Muslim Brotherhood, and human rights groups said campaigning for a "no" vote had been repressed.
The draft constitution deletes Islamic language written into the basic law approved a year ago when Mursi was still in office. It also strengthens the state bodies that defied him: the army, the police, and the judiciary.
Sisi, who deposed Mursi after mass protests against his rule, appeared to link a decision on his presidential bid to the result. Analysts say his candidacy appears to be a foregone conclusion.
Officials have not indicated when the results of the poll will be announced.
The army-backed authorities said turnout was strong, but supporters of the jailed Mursi's Muslim Brotherhood said their calls for a boycott of a "sham" vote had been observed.
The Cairo Institute for Human Rights criticised Egyptian media for "stoking hatred towards the Brotherhood" and contributing to a climate of intimidation.
At many polling stations across the Arab world's most populous country, the referendum could have been mistaken for a vote on Sisi himself.
Women chanted his name and ululated as they stood in line to vote, while a pro-army song popularized after Mursi's overthrow blared from cars.
The referendum is a key step in the political transition plan the interim government has billed as a path to democracy as it continues to take fierce measures against the Brotherhood, Egypt's best organised party until last year.
The government last month declared the group to be a "terrorist organisation". Al Qaeda-inspired militants have stepped up attacks on security forces since Mursi's removal.
A presidential election could be held as early as April.
High turnout would be seen as a strong stamp of approval for the new political order, which could see the return of military men to power - resuming the six-decade tradition in the country until the 2011 uprising against president Hosni Mubarak.
Turnout was about 30 percent in the 2012 referendum on the Islamist-tinged constitution adopted during Mursi's year in office.
"God willing a large percentage of the public will vote 'yes', and for one main reason - we have been through great hardship and been worn out", said Hisham Mohamed Moussa, waiting to vote in Cairo.
While Western states have criticised the crackdown and called for inclusive politics, they have put little pressure on Cairo. Egypt, which controls the Suez Canal, has been a cornerstone of U.S. policy in the Middle East since the 1970s, when it became the first Arab state to make peace with Israel.
The U.S-based Carter Centre, which has monitored most of the votes held over the past three years of political upheaval, sent only a small observation mission after voicing concern at "narrowed political space" around the vote.
Another U.S-funded group, Democracy International, had 83 observers deployed across the country. DI Programme Manager Dan Murphy told Reuters observers were reporting that "from a technical standpoint the process is proceeding normally".
The Carnegie Endowment for International Peace in Washington warned that international players risked lending legitimacy to a "flawed and undemocratic progress".