Polls across Egypt have closed 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 yesterday, when nine people were killed, but officials said police arrested at least 79 people during protests by supporters of deposed President Mohamed Mursi, removed from power in July.

The Interior Ministry said 444 people had been arrested for "obstructing the referendum process" over the two-day vote.

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 Mr 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.

Mr Sisi, who deposed Mr 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, but High Elections Commission spokesman Hisham Mokhtar told Reuters that according to the law, they must be announced within 72 hours of polls closing.

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.

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 Mr Mursi's removal.

A presidential election could be held as early as April.

The US-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 US-funded group, Democracy International, had 83 observers deployed across the country. DI Programme Manager Dan Murphy said 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."