RIYADH, Saudi Arabia — One day in November 2015, Saad Almadi typed out a 14-word post on Twitter about Saudi Arabia’s deputy crown prince.
“Mohammed bin Salman has taken over the economy, defense and everything under the king,” he wrote, replying to a professor who is a fierce critic of the kingdom’s monarchy.
A Saudi-American dual citizen living in Florida, Mr. Almadi had little reason to believe his post would attract attention. He was a retired project manager, not an activist, and his words were largely factual — Prince Mohammed had taken control of many of the levers of power since his father became king that year. By 2017, he would push aside a cousin to become heir to the throne.
Yet the tweet resurfaced as evidence seven years later when Mr. Almadi, 72, was arrested during a visit to Saudi Arabia. Along with other Twitter posts he wrote that were critical of the Saudi government — and an “insulting picture” of Prince Mohammed saved on his phone — the tweet was cited as proof that he had “adopted a terrorist agenda by defaming symbols of the state” and “supported terrorist ideology,” according to court documents.
His prosecutor requested a severe punishment, “to rebuke him and deter others.” In October, Mr. Almadi was sentenced to 16 years in prison, lengthened on Feb. 8 to 19 years after he appealed.
“My father is nowhere near being a dissident,” said his son, Ibrahim Almadi, describing him as an open-minded man who spent his retirement traveling, hiking and wine tasting. Now he is being held in Al-Ha’ir prison, a facility in the Saudi capital, Riyadh, that houses members of Al Qaeda alongside political activists.
Saudi Arabia has always been an authoritarian monarchy with limited freedom of speech. But 10 years ago, Mr. Almadi’s Twitter account, which has fewer than 2,000 followers, might have prompted a warning or an interrogation. Under Prince Mohammed, now prime minister, harsher punishments are being meted out to citizens who criticize their government, while the defendants on trial have become increasingly less prominent.
“The scope of oppression really is unprecedented,” said Hala Aldosari, a women’s rights activist who left Saudi Arabia in 2014 for a postdoctoral fellowship in the United States and said she never felt safe enough to return.
Since then, Prince Mohammed has rendered the conservative Islamic kingdom nearly unrecognizable, setting in motion seismic changes — some of which activists like Ms. Aldosari spent years campaigning for.
He launched an ambitious plan to diversify the oil-dependent economy and ended a slew of religious and social restrictions that many Saudis found suffocating. Women, barred from driving until 2018, now work as Amazon delivery drivers, chief executives and ambassadors. Music, once effectively prohibited in public, thumps inside dimly lit restaurants where young couples flirt. The gender segregation that shaped public life for decades has dissolved.
At the same time, the modest space for political discourse has shriveled.
“It’s a bittersweet moment in history, where you see the fruits of your mobilization somehow yielded, but for the wrong reason,” Ms. Aldosari said. “The people are being shut down or silenced in return for giving them certain rights.”
Since 2017, the Saudi authorities have arrested hundreds of public figures across the political spectrum, including Snapchat influencers, religious clerics, billionaires and several of the prince’s own cousins. The killing in 2018 of the Washington Post columnist Jamal Khashoggi by Saudi agents in Istanbul, prompting international outrage, was the most dramatic example of a broader crackdown that has continued to deepen since his death.
The authorities have paid special attention to Twitter, which is widely used in the kingdom.
Noura al-Qahtani, who ran an anonymous Twitter account, was among several people put on trial last year in relation to social media activity. On her account, where she had roughly 600 followers, she called for anti-government protests, criticized some social liberalization measures and wrote that Prince Mohammed was “not good enough to be a prince.”
After a court found her guilty of “challenging the faith and justice of the king and the crown prince” and “supporting the ideology of people who strive to disturb public order,” among other charges, she was sentenced to 13 years in prison. On appeal, she pleaded for mercy, saying that she was nearly 50 and had five children to take care of, according to a copy of her verdict. Instead, the panel of judges lengthened her sentence to 45 years in prison.
Around the same time, Salma al-Shehab, a Saudi doctoral student at Leeds University in Britain, was sentenced to 34 years in prison, largely in relation to following Saudi dissidents on Twitter and sharing their posts, according to a copy of her verdict.
The court sentenced both women under counterterrorism and cybercrime laws. Both were given an additional penalty at the discretion of the judges.
A Saudi official said in a statement to The New York Times that the government was studying and putting new measures in place to enhance human rights, including changes to the judicial system. However, Saudi Arabia “maintains a zero-tolerance policy when it comes to terrorism,” the official said,speaking on the condition of anonymity in line with government protocol.
The official did not respond to questions about specific prisoners, including Mr. Almadi, Ms. al-Qahtani and Ms. al-Shehab, saying only that “cases of individuals that violate national laws are clearly differentiated from peaceful expressions of opinion.”
Yet a review of the detainees’ Twitter accounts — which were the basis for their indictments — did not reveal posts professing support for militant groups or endorsing violent action, aside from a vague tweet by Ms. al-Qahtani that referred to “removing this tyrant from the face of the earth,” without mentioning a name. Instead, their prosecutors cited posts critical of the government or royal family members and labeled them terrorism-related views that threatened state security, according to court documents.
Until recently, prison sentences longer than 20 years were rare in the kingdom, and Saudis with American citizenship or ties to local elites, like Mr. Almadi, would have been able to draw on connections to protect themselves.
“One of the merits of Mohammed bin Salman is that he’s created equality of injustice for all,” said Taha al-Hajji, a Saudi lawyer who lives in exile in Germany.
The “red lines” that curbed freedom of expression were also more obvious under previous rulers: the royal family, the king, Islam. Now, many people have “absolutely no idea” what is permissible, said Hussein Ibish, a senior resident scholar at the Arab Gulf States Institute in Washington.
“It’s designed to create a climate of intimidation, at the political register, which is meant to inoculate the regime,” he said.
In an interview in 2018, Prince Mohammed denied creating an atmosphere of fear. If he had, he added, it was “a small price” to pay to “get rid of extremism and terrorism without civil war, without stopping the country from growing, with continuous progress in all elements.”
Many Saudis are deeply disturbed by the crackdown, even if it has not touched them personally. And yet the rapid transformation of their country offers plenty of rewards and distractions that have also been widely welcomed. High oil prices last year helped the economy grow by more than 8 percent, the fastest rate among the Group of 20 industrialized nations.
“The kingdom is in a sensitive historical transformation phase in all aspects,” said Salman Al-Ansari, a Saudi political analyst. “No one can deny the speed in which the reforms are taking place. But like anything else, reforms come with a cost.”
Some Saudis believe the trade-off is worth it. To others, including Ms. Aldosari, it is a betrayal.
“This is not what we aspired to,” she said. “We aspired for a community where we are heard, where we are seen, we are respected and we are included in decision-making.”
Ms. Aldosari blamed American and European foreign policies for the escalation in repression, saying that foreign governments had elevated other goals — like getting Arab governments to normalize relations with Israel, or securing stable oil markets — at the expense of human rights.
The Biden administration pledged to put human rights “at the center” of American foreign policy. When President Biden visited Saudi Arabia last summer and shared a fist-bump with Prince Mohammed, Saudi dissidents saw it as a retreat.
“Advancing human rights in Saudi Arabia is a key priority for the United States,” the State Department said in a statement, noting that U.S. officials “regularly raise” cases, including those of Mr. Almadi, Ms. al-Shehab and Ms. al-Qahtani, with Saudi officials. “We continue to have significant concerns with the imposition of severe sentences for the exercise of freedom of expression.”
There are also a growing number of Saudis living in exile in the United States, unable to reunite with their families. Among them is Maha al-Qahtani, whose husband, Mohammed al-Qahtani, was once a prominent Saudi political activist. (They are not related to Noura al-Qahtani.)
An economics professor, Mr. al-Qahtani co-founded an independent human rights organization in 2009. In 2013, he was sentenced to 10 years in prison.
Maha al-Qahtani eventually settled in the United States with their five children, counting the years until her husband’s sentence ended in November.
In October, they were preparing for his release, gathering the gifts they bought while he was in prison, when Mr. al-Qahtani stopped calling home. Maha al-Qahtani sought help from every authority she could reach out to, but found no explanation. Mr. al-Qahtani has effectively disappeared.
“This is the father of my children, my husband, my love,” she said in a phone interview, her voice breaking. “Where are you?”
Karen Zraick contributed reporting from New York.