CAIRO — Egyptian lawmakers on Tuesday approved sweeping changes in the country’s constitution to extend President Abdel Fatah al-Sissi’s rule and give him unprecedented powers, cementing his authoritarian grip on the Arab world’s most populous nation.

The vote — 531 to 22, with one abstention — was widely expected: The legislature is dominated by Sissi’s loyalists, and his regime has largely silenced opposition to the constitutional amendments, arresting dissenters and seeking to stamp out an online protest campaign by shutting down its website. It also has taken steps to restrict online content that allowed Egyptians access to the opposition campaign.

The amendments, which were pushed through parliamentary hearings and debates over a few weeks, will now be put to a public referendum, a three-day process that could begin as early as next week. But critics say an equitable vote is unlikely.

“We know that the vast majority of Egyptians do not support these amendments, but a free and fair vote will be almost impossible,” Dina Darwish, an Egyptian American physician and activist, said in a statement. “Many Egyptians fear for what will happen if they do not support Sissi. When a vote is based on fear, it is not a democratic vote.”

If a majority of Egyptians vote in favor, it would extend presidential terms to six years. So Sissi’s current term would be extended by two more years, and he would be permitted to run once again in 2024. That means, in theory, that he could remain in power until 2030.

When President Trump, during a meeting with Sissi last week at the White House, was asked about what human rights groups call a power grab in Egypt, Trump described Sissi as “a great president” and said that “he’s doing a great job.”

Sissi also would be given new powers to appoint judges as well as the public prosecutor, in effect gaining control over the judiciary. The proposed changes also include amending the constitution to state that the role of the military, which Sissi once led and which remains the force behind his presidency, is to protect “the constitution and democracy.”

The measures to bolster Sissi’s influence stand in sharp contrast to the populist revolts in Algeria and Sudan that have toppled long-ruling dictators in recent weeks and now are seeking to oust the entire political and military elites in their nations.

If the constitutional changes are approved in the referendum, Sissi’s critics fear that his government — already considered the most authoritarian in Egypt’s modern history — will only escalate its ongoing evisceration of freedoms, rights and the rule of law. Sissi’s regime has jailed tens of thousands of critics and opponents, all but obliterated independent media and shut down hundreds of websites deemed critical of his presidency.

“These amendments all serve the benefit of one man, a one-man’s rule” said a 39-year-old doctor who spoke on the condition of anonymity because he fears becoming a target of the regime.

Sissi’s supporters insist that his tenure needs to be extended to allow him time to implement economic reforms, finish large development projects including the construction of a new administrative capital, and fight terrorism, notably an active Islamic State branch centered in the country’s northern Sinai region.

“There has to be an infrastructure in the country for the youth to have a better future,” said Ahmad Abdel Baqy Metwally, 62, a retired government employee. “I want Sissi to continue because he is an expert on security. Had not it been for him, we would have been living in chaos and massacres now.”

Sissi became president in 2014, a year after he led a military coup that toppled Egypt’s elected Islamist leader, Mohamed Morsi. In 2018, Sissi was reelected in a vote in which all of his credible opponents were driven out of the contest through arrests, intimidation or the absence of a level playing field.

More than a week ago, posters and banners emerged across Cairo and other cities urging Egyptians to vote yes in the referendum — even though no date has yet been set. Many were emblazoned with Sissi’s visage, with a bright-red check mark next to it.

“Yes to the constitutional amendments for a better future for Egypt,” read one banner.

In several drives around Cairo in recent days, not a single “No” poster could be seen. Egypt’s weak opposition and pro-democracy activists say they have been blocked from openly campaigning.

This month, leading Egyptian opposition figures launched an online campaign called Batel, which in Arabic means “void,” to give Egyptians a forum to oppose the proposed changes. But a day after the online petition was launched — it had reached 60,000 signatures within 12 hours, its organizers said — the government blocked the website.

The site could still be accessed from abroad and through a VPN or an encrypted messaging app, however. By Tuesday, the number of signatures had reportedly reached more than 250,000.

Then the Sissi government blocked or partly blocked 34,000 more websites and domain names to prevent Egyptians from joining the “void” campaign, according to NetBlocks.org, an independent, nonpartisan civil society group working for digital rights and freedoms.

“Thirty-four thousand domains blocked by Egypt to prevent opposition to a referendum. There is no legitimacy, just brute force,” Wael Eskandar, a well-known Egyptian blogger and activist, said in a tweet Tuesday.

Many of Sissi’s opponents fear the worst if the “Yes” voters prevail.

“We are concerned that these constitutional amendments will be the final step toward transforming Egypt into a fully autocratic state, with extreme human rights violations and failures in all aspects of life for many years to come,” Ayman Nour, a leading opposition politician living in exile in Turkey, said in a statement.

“The amendments would end any hope for a safe transition of Egypt to democracy and would take Egypt to decades of failure and instability,” he wrote.