Egypt's opposition on Sunday called for mass street protests on Tuesday rejecting a December 15 referendum on a new constitution largely drafted by President Mohamed Morsi's Islamist allies.

"We do not recognize the draft constitution because it does not represent the Egyptian people," the opposition National Salvation Front said in a statement read out at a news conference by spokesman Sameh Ashour.

Egyptian F-16 fighter jets made low passes over the center of Cairo on Sunday in a rare maneuver by the air force over the capital amid high political tension, AFP correspondents reported.

The military was not immediately available for comment.

Egyptian President Mohamed Morsi on Saturday annulled a decree he issued last month expanding his powers, an official told a Cairo news conference.

"The constitutional decree is annulled from this moment," said Selim al-Awa, an Islamist politician acting as spokesman of a meeting Morsi held earlier with other political leaders.

Egypt's main Islamist parties, including President Mohamed Morsi's Muslim Brotherhood, rejected on Saturday opposition demands to delay a December 15 referendum on a new constitution they helped draft.

The 13 parties "insist that the referendum on the constitution take place on the scheduled date, with no modification or delay," according to a joint statement read to media by the number two of the Muslim Brotherhood, Khairat al-Shater.

The African Union on Saturday called for dialogue in Egypt over the Islamist-led government plan for a referendum on a draft constitution, which opposition activists oppose..

AU chairperson Nkosazana Dlamini-Zuma "underscores the imperative for all the parties to engage in dialogue and to work towards an inclusive constitution making process", said an AU statement.

Calm was restored to Egypt on Saturday as the powerful military threw its weight behind dialogue to resolve the political crisis dividing the nation, warning it would "not allow" events to take a "disastrous" turn.

A mass overnight protest against President Mohammed Morsi ended peacefully, but the underlying political crisis dividing the country persisted.

French and Italian archaeologists have found the remains of a grain port that played a critical role in the rise of ancient Rome, France's National Center for Scientific Research (CNRS) said on Thursday.

Cores drilled at a location at the mouth of the River Tiber have revealed the site of a port whose existence has been sought for centuries, it said in a press release.

Egyptian authorities have detained a suspected terror network ringleader whose operatives are believed to have carried out a deadly attack on a U.S. mission in Libya, a report said Friday.

Mohammed Jamal Abu Ahmed -- a former member of the Egyptian Islamic Jihad, who was freed from prison in March 2011 following the ouster of Egyptian leader Hosni Mubarak -- was captured in the past week, the Wall Street Journal reported, citing unnamed U.S. officials.

A prominent opposition leader on Friday stressed preconditions for any dialogue with President Mohamed Morsi to ease Egypt's dire political crisis, notably that Morsi postpone a referendum on a new constitution.

Mohamed ElBaradei, a former U.N. atomic agency chief and Nobel peace prize winner, also called on Morsi to "repeal the decree" announced two weeks ago giving him sweeping new powers, saying "he can do this immediately, tonight."

U.N. human rights chief Navi Pillay on Friday criticized Egypt's draft constitution and expressed sympathy for those protesting the way it had been drawn up.

"I believe people are right to be very concerned," Pillay said Friday, pointing to "the way the process has been short-circuited," as well as "some of the elements included in, or missing from, the draft text."