Egyptian Islamist Mohammed Morsi has declared victory in the country's first post-uprising presidential election, but his establishment-backed rival Ahmed Shafiq disputed the claim as Egypt's military rulers expanded their powers over the next president.

Mr. Morsi's Muslim Brotherhood movement said unofficial results show he won about 52 percent of the vote in the two day run-off election that ended Sunday, compared to 48 percent for Mr. Shafiq, the last prime minister to serve under ousted president Hosni Mubarak. The Brotherhood based its victory claim on results tallied by Brotherhood representatives at almost all of the country's the polling stations.

In a speech at his campaign headquarters Sunday, Mr. Morsi said he will serve as a leader of all Egyptians, both Muslims and Christians, and promised not to “seek revenge or settle accounts” with opponents of the Islamist group.

“We are seeking stability, love and brotherhood for an Egyptian state that is civil, national, democratic, constitutional and modern. We all are looking forward to love each other.”

A Shafiq aide expressed astonishment at the Brotherhood's announcement. Mahmud Barakeh accused the Islamists of “hijacking” the election process by refusing to wait for the election commission's official results, which are due by Thursday. Barakeh also said the Shafiq campaign's unofficial figures put the former prime minister in the lead.

In a move that diminishes the powers of the eventual election winner, Egypt's ruling generals declared a new interim constitution just after the polls closed on Sunday. The military council has led the country since Mubarak's ouster in March 2011 and had promised to hand over power to a newly-elected president by July 1.

Western news agencies said the interim constitution grants the generals legislative powers until a new lower house of parliament is elected to replace the Islamist-dominated People's Assembly elected earlier this year and dissolved by the country's top court last week. Under the document, expected to be published on Monday, no election can be held until a military-appointed panel writes a permanent constitution whose articles the generals can veto.

As the Muslim Brotherhood celebrated what it considered to be Mr. Morsi's election victory, it also rejected the military's interim constitution, raising the prospect of a confrontation between the two sides.

The Brotherhood-affiliated speaker of Egypt's dissolved People's Assembly, Saad el-Katatni, said a panel appointed by the body last week will go ahead with plans to write a permanent constitution. The Muslim Brotherhood has refused to recognize the dissolution of parliament.

Turnout in the two-day presidential runoff appeared lower than the 46 percent figure reported in last month's first round – a sign of declining public morale as the military tightened its grip on power in recent days.

The lack of interest in the vote also reflected public dissatisfaction with the choice of candidates. Mr. Shafiq is a former air force general and Mubarak aide who promised to restore order to Egypt and push back against the rise of Islamism. Mr. Morsi represents the once-outlawed Muslim Brotherhood, a religious party committed to reversing liberal social traditions.

Some voters told VOA they preferred the centrist candidates eliminated in the first round. They said they cast ballots against Mr. Morsi and Mr. Shafiq in a show of protest.