In Washington, the Republican chairwoman of the Foreign Affairs Committee in the US House of Representatives, Ileana Ros-Lehtinen, called the vote "a defeat for the Egyptian people".
"We cannot celebrate the trade of an authoritative regime for an Islamic dictatorship," she said.
Victory for Islamist
The passage of the constitution would be a victory for Morsi. The FJP, the Brotherhood's political arm, said that it hoped the passage is a "historic opportunity" to heal Egypt's divisions and launch a dialogue to restore stability and build state institutions.
But the comparatively low turnout of 32 percent of eligible voters, as well as allegations by the opposition of voting violations, threatened to undermine the constitution's legitimacy and keep Egypt polarized.
Aside from a vocal opposition, Morsi is also facing a fragile economy, weathered by nearly two years of political turmoil and accompanying violence as well as nearly a month of political crisis that preceded the vote.
Saturday's voting in 17 of Egypt's 27 provinces was the second and final round of the referendum. Preliminary results released early by Morsi's Muslim Brotherhood showed that 71 percent of those who voted on Saturday said "yes", after 99 percent of polling stations were accounted for. Only about eight million of the 25 million Egyptians eligible to vote - a turnout of about 30 percent - cast their ballots, a significantly lower number than those who voted in most previous presidential and parliamentary elections.
The opposition said that even though it is challenging the results of the referendum, it will continue to prepare for the parliamentary elections.
Sunday editions of Egyptian newspapers reflected the divisions in the country.
"Egypt heads to stability," read the front-page headline in state-owned Al-Akhbar.
"Mass violations," the mass circulation independent daily Al-Masry al-Youm reported.
The head of the Brotherhood's FJP, Saad al-Katatni, offered an olive branch to other parties on Saturday, saying in a statement the party hopes "to turn over a new leaf" in the political confrontation.
AFP-AP