Egypt's controversial Islamist-backed constitution has been approved, according to preliminary referendum results released by the country's Muslim Brotherhood today.

The results, posted on the Brotherhood's website, showed the disputed constitution had a Yes majority of more than 70% in yesterday's second and final round of voting.

The referendum was held over two days, on December 15 and yesterday. In the first round, about 56% said Yes to the charter. The turnout then was about 32%. Yesterday's turnout was about 30%.

The Brotherhood, of which Islamist President Mohammed Morsi hails, has accurately predicted election results in the past by tallying results provided by its representatives at polling centres. Official results will not be announced for several days.

The Yes vote was a victory for Islamist president Mohammed Morsi, but a costly one. The bruising battle over the past month stripped away hope that the long-awaited constitution would bring a national consensus on the path Egypt will take after shedding its autocratic ruler Hosni Mubarak nearly two years ago.

Instead, Mr Morsi disillusioned many non-Islamists who had once backed him and has become more reliant on his core support in the Muslim Brotherhood and other Islamists.

Hardliners in his camp are determined to implement provisions for stricter rule by Islamic law in the charter, which is likely to futher fuel divisions.

His liberal and secular opposition, in turn, faces the task of trying to organise the significant portion of the population angered by what they see as attempts by Mr Morsi and the Brotherhood to gain a lock on political power.

The main opposition group, the National Salvation Front, said it would now start rallying for elections for the next law-making, lower house of parliament, expected early next year.

"We feel more empowered because of the referendum. We proved that at least we are half of society (that) doesn't approve of all this. We will build on it," the party's spokesman, Khaled Daoud, said. But, he said, there was "no appetite" at the moment for further street protests.

Yesterday's voting in 17 of Egypt's 27 provinces was the second and final round of the referendum. The new constitution will come into effect once official results are announced, expected in several days.

In a sign of disarray in Mr Morsi's administration, his deputy and - possibly - the Central Bank governor resigned during yesterday's voting.

Vice President Mahmoud Mekki's resignation had been expected since his post is eliminated under the new constitution. But its hasty submission even before the charter has been sealed and his own resignation statement suggested it was linked to Mr Morsi's policies.

"I have realised a while ago that the nature of politics don't suit my professional background as a judge", his resignation letter, read on state TV, said.

Mr Mekki said he had first submitted his resignation last month but events forced him to stay on.

The status of Central Bank governor Farouq el-Oqdah was murkier. State TV first reported his resignation, then soon after said the Cabinet denied he had stepped down.

Mr El-Oqdah, in his post since 2003, has reportedly been seeking to step down but in recent weeks the administration was trying to convince him to stay on.

The government is eager to show some stability in the economy as the Egyptian pound has been sliding and a much-needed £3 billion loan from the International Monetary Fund has been postponed.

Over the past month, seven of Mr Morsi's 17 top advisers and the one Christian among his top four aides have resigned.

Like Mr Mekki, they said they had never been consulted in advance on any of the president's moves, including his November 22 decrees, since rescinded, that granted himself near absolute powers.

Those decrees sparked large street protests by hundreds of thousands around the country, bringing counter-rallies by Islamists.

The turmoil was further fuelled with a Constituent Assembly almost entirely made up of Islamists finalising the constitution draft in the dead of night amid a boycott by liberals and Christians.

Rallies turned violent, Muslim Brotherhood offices were attacked, and Islamists attacked an opposition sit-in outside the presidential palace in Cairo leading to clashes that left 10 dead.

The turmoil opened up a vein of bitterness that the polarising constitution will do little to close.

Morsi opponents accuse him of seeking to create a new Mubarak-style autocracy and the Brotherhood accuse his rivals of being former Mubarak officials trying to topple an elected president and return to power.

Islamists branded opponents "infidels" and vowed they would never accept anything but "God's law" in Egypt.

Both rounds of voting saw claims by the opposition and rights groups of voting abuses ranging from polling stations opening late to Islamists seeking to influence voters. The official MENA news agency said at least two judges were removed for coercing voters to cast Yes ballots.