The government says the 34 amendments are part of a reform process, but the opposition and activist groups call them a move away from freedom and democracy.
Egyptian President Hosni Mubarak says the reforms will prevent Islam from being misused for political purposes. The most controversial proposal is a ban on religion-based political parties.
That has the Muslim Brotherhood, the main opposition party, calling for a boycott. The Islamist group sees itself as the main target of the proposed changes. The party, which won a fifth of the seats in parliament in 2005, has said that voting in the referendum is pointless as the government will fix the results anyway.
Calls For A Boycott
But all major opposition groups -- including secular liberals -- are calling for a boycott.
"Don't cooperate with this farce," a speaker told a demonstration in Cairo said today. "We will punish everyone who takes part in this farce which rises to the level of treason."
The crowd then began chanting, "Don’t participate!"
The proposed changes, rushed through the ruling party-dominated parliament only a week ago, have even drawn rare U.S. criticism.
Washington, which has made democratic reform in the Middle East a key policy goal, expressed concern last week that Egypt was not taking the regional lead on greater openness and pluralism.
But Secretary of State Condoleezza Rice, visiting Egypt on March 25, tempered U.S. criticism, telling a Cairo news conference that Egypt has to chart its own reform path, one that is appropriate to its "culture."
Not everyone in Egypt is critical, either.
"It is a very good initiative and very civilized, and it helps people express their opinions, either yes or no," a Cairo voter identified as Youssef told journalists today. "People should be positive and come and participate, whether they accept or reject it."
Off To A Slow Start
Egyptians began going to the polls early today. But early turnout was reportedly low, amid heavy traffic and a massive security lockdown.
Almost two hours into voting in a large school in the Mediterranean city of Alexandria, officials said 53 out of 3,576 registered voters had voted -- about 1.5 percent.
In the central Cairo district of Garden City, only two voters were present at one polling station in mid-morning.
Some 35 million people are eligible to vote at some 30,000 polling stations.
In the first major constitutional changes in 26 years, Mubarak last December asked parliament to amend 34 articles of the constitution as part of a package of political reforms.
But in the referendum, voters are not given a choice on the individual changes. Instead, they must vote for or against the entire package of amendments. One change allows authorities to arrest terrorism suspects without a warrant and to refer them to military courts. Another reduces judicial oversight of elections.
Lack Of Awareness
Still, some say ordinary Egyptians are simply not aware of what is stake in today’s vote.
“A huge majority of the Egyptian people don't know anything about the constitutional amendments," a Cairo voter identified as Emad told Reuters today. "There should have been an information campaign ahead of this referendum. There was none."
Still, critics say the changes mean citizens would no longer be protected from encroachments by state authorities, and that opportunities for political participation would be even more limited than they are now.
Muslim Brotherhood leaders say the government's aim is to push the Islamists out of the way and make it easier to install Mubarak's son, Gamal, as the country's next president.
The London-based rights watchdog Amnesty International, for its part, has described the changes as the "greatest erosion of human rights in 26 years."
(with material from Reuters, AFP, dpa)