NEW YORK ( TheStreet) -- Egypt's Islamist-supported constitution passed a national referendum, the country's election commission announced Tuesday. The constitution received the support of 63.8% of those who voted, but only 32.9% of registered voters turned out. That was a significantly lower turnout than in other elections since a popular uprising forced the ouster of former leader Hosni Mubarak in 2011, CBS News reported on its Web site. Egypt's Muslim Brotherhood, the primary group supporting the constitution, cheered the outcome. "Let's all begin to build the renaissance of our country with free will, good intentions and strong determination, men, women, Muslims and Christians," wrote the group's leader, Mohammed Badie, on Twitter, CBS News reported. The opposition, which had staged massive street protests against the proposed constitution, has vowed to challenge the results of the referendum, CBS News added. Opposition members fear that the constitution will pave the way to Islamic rule in Egypt.