In a reversal of fortunes unthinkable a year-and-a-half ago, an Islamist jailed by Hosni Mubarak has succeeded him as president of the biggest Arab nation in a victory that will have historic consequences for Egypt and the Middle East.

The Muslim Brotherhood's Mohamed Morsy will not enjoy the modern pharaonic powers exercised by Mubarak: those have been curtailed by a military establishment that will decide how much he will be able to do in government.

But the US-trained engineer's victory in the country's first free presidential election breaks a tradition of domination by men from the armed forces, which have provided every Egyptian leader since the overthrow of the monarchy 60 years ago, and installs in office a group that drew on 84 years of grassroots activism to catapult Morsy into the presidency.

He has promised a moderate, modern Islamist agenda to steer Egypt into a new democratic era, in which, he promises, autocracy will be replaced by a transparent government that respects human rights and revives the fortunes of a powerful Arab state long in decline.

Morsy also promised an "Egyptian renaissance with an Islamic foundation".

The stocky, bespectacled 60-year-old was flung into the race at the last moment by the disqualification of Khairat al-Shater, the group's preferred choice.

Questions remain about the extent to which Morsy will operate independently of other brotherhood leaders once in office: his manifesto was drawn up by the group's policy-makers. The role Shater might play has been a focus of debate in Egypt.

"I will treat everyone equally and be a servant of the Egyptian people," Morsy said in Cairo shortly after polling ended.

But many Egyptians, not least the Christian minority, remain suspicious of Morsy, and even more so of the group he represents.

Anti-brotherhood sentiment, fuelled by both a hostile media and some of the group's policies, has soared in recent weeks.

Ahmed Shafik, the former general Morsy defeated, won nearly as many votes as he, signalling that Egypt is a nation that is anything but united around the idea of brotherhood rule.

At first, Morsy pitched himself as a conservative Islamist - the only one in the field, he said. He repeatedly promised to implement Islamic law in speeches peppered with references to God, Mohammed and the Koran.

"It was for the sake of the Islamic sharia that men were ... thrown into prison. Their blood and existence rests on our shoulders now," Morsy said at one of his early campaign rallies.

Though not one of those jailed for years, he was held on more than one occasion by Mubarak's feared state security service.

But he has seldom spelt out what precisely his call to implement sharia, or Islamic law, would mean for Egypt, where piety runs deep and the constitution already defines the principles of the sharia as the main source of legislation.

Pushed by a TV interviewer to clarify what Islamist rule might mean for bikinis on Red Sea beaches - and so for Egypt's vital tourist industry - Morsy equivocated.

He described such issues as "very marginal, very superficial and affecting a very limited number of places", adding that sector specialists must be consulted on all draft laws.