Egyptians are voting in a two-day referendum to decide whether to adopt a new constitution supported by the military-backed interim government.
The vote is seen as a referendum on a likely presidential run by the country's army chief, Adbel Fattah al-Sisi, who ousted former president Mohamed Morsi in July.
Shortly before the polls opened, a bomb exploded outside a courthouse in Giza. No casualties were reported.
A group that includes Mr. Morsi's Muslim Brotherhood urged Egyptians to boycott the referendum and hold peaceful protests against a process they have called illegitimate.
Analysts predict the constitutional referendum will easily pass.
Saba Mahmood, associate professor of anthropology at the University of California at Berkeley told VOA she expects the document to be ratified by a "broad referendum."
"I think this is the result of two things. One is the political repression that the military government has unleased in Egypt so that most people who disagree with the government are not going to really come out in any great numbers because they are afraid of the political repercussions. And secondly, there is a general nationalist fervor that has gripped the country in support of the military."
The constitutional referendum comes about a year after Mr. Morsi signed the last constitution into law. The new proposed charter would strip out Islamist language in the existing document, give women greater rights and strengthen the power of the military.
A roadmap set by the military calls for parliamentary and presidential elections to follow later this year.
In Washington, the U.S. State Department Monday expressed concern about reports that people campaigning for a 'no' vote have been arrested.
A spokeswoman said the United Sates is deeply troubled by reports that at least one individual was beaten during his arrest.
Egyptians living abroad already have voted on the new constitution.
The military removed Mr. Morsi from power after opposition protests that accused him of trying to monopolize power. Authorities have since spent months cracking down on the Muslim Brotherhood, including arresting many of its leaders and declaring it a terrorist group.
More than 1,000 people, mainly pro-Morsi Islamists, have been killed, while protests continue.