- Approval of Egypt's controversial draft constitution in an initial round of voting revealed the grass-roots power of Islamists even as the popularity of President Mohamed Morsi has dimmed in this increasingly polarized and struggling nation.

Unofficial results reported by state media from Saturday's constitutional referendum indicated that the Islamist-backed draft charter passed with about 56 percent of the vote in 10 of Egypt's 27 governorates. The results were immediately challenged by mainly secular opponents of the Morsi government, who cited thousands of alleged voting abuses and irregularities.

While not a sweeping mandate, the outcome suggests that Morsi, a religious conservative, and his political allies in the Muslim Brotherhood rallied their base around a constitution that may gradually open the country to the influence of sharia, or Islamic law.

Official results will be announced after the results of second and final round of voting Saturday in the remaining 17 governorates are examined. The momentum of the early results, however, indicates that the constitution is likely to be adopted. The final round moves to regions traditionally loyal to the Brotherhood and ultraconservative Salafis.

"Egyptians have spoken their mind," the Brotherhood's political wing, the Freedom and Justice Party, said in a statement. "The people have expressed their free will in the first stage of the constitutional referendum and have also proved to be highly aware. This is a genuine democratic process."

The main opposition National Salvation Front accused the Morsi government and the Brotherhood of rigging the referendum. In a statement Sunday, the opposition group urged the commission overseeing the vote to investigate more than 7,000 alleged irregularities, including lack of judicial supervision.

The movement said the government urged its supporters to "terrorize and intimidate the opposition." It called on Egyptians to demonstrate Tuesday "to defend their free will and ... end this draft constitution, which is considered to be illegal."

Egyptian human-rights organizations demanded that the referendum's first round be repeated. They alleged a number of violations and abuses, including instances in which women, some of them Christian Copts, were refused ballots.

Violent protests and unrest in the weeks leading to the referendum exposed an Egypt desperate for stability but caught in a volatile struggle between Islamists and the mainly secular opposition.