Egyptian President Mohammed Mursi has signed into law a new constitution shaped by his Islamist allies.

It is a bitterly contested document which he insists will help end political turmoil and allow him to focus on fixing the economy.

Anxiety about a deepening political and economic crisis has gripped Egypt in past weeks.

Many people have been rushing to buy dollars and withdraw their savings from banks.

The Egyptian pound tumbled today to its weakest level against the US currency in almost eight years. 

The liberal opposition says the new constitution betrays Egypt's 2011 revolution.

The opposition claims that the constitution dangerously mixes religion and politics.

They say it has polarised the Arab world's most populous nation and prompted occasionally violent protest on the streets.

The presidency said that Mr Mursi had formally approved the constitution the previous evening, shortly after results showed that Egyptians had backed it in a referendum.

The text won about 64% of the vote, paving the way for a new parliamentary election in about two months.

The charter states that the principles of sharia, Islamic law, are the main source of legislation.

It says that Islamic authorities will be consulted on sharia - a source of concern to the Christian minority and others.

The referendum result marked yet another electoral victory for the Islamists since veteran autocrat Hosni Mubarak was toppled in 2011.

Mr Mursi's government has accused opponents of damaging the economy by prolonging political upheaval.

It now faces the tough task of building a broad consensus as it prepares to impose austerity measures.

The opposition has condemned the new basic law as too Islamist.

It says it could allow clerics to intervene in the lawmaking process and leave minority groups without proper legal protection.

The opposition claims this month's vote was marred by major violations.

Nevertheless, major opposition groups have not called for new protests, suggesting that weeks of civil unrest over the constitution may be subsiding now that it has passed.