LONDON — A popular imprisoned Saudi cleric who called for reform in the Gulf kingdom could be sentenced to death this weekend, activists warned Friday.

Salman al-Awda, who said the country's rulers should be more responsive to the population's desires, is due to stand trial in the country’s anti-terror court Sunday, according to the rights group Amnesty International. The public prosecutor has called for him to be sentenced to death.

"We are gravely concerned that Sheikh Salman al-Awda could be sentenced to death and executed," Lynn Maalouf, Amnesty International’s Middle East research director, said in a statement.

Saudi officials were not immediately available for comment.

Swept up in Saudi Crown Prince Mohammed bin Salman's crackdown on perceived critics and those calling for political reform, al-Awda could now pay the ultimate price for speaking out against the regime.

"They are making an example of him for standing up to the system politically," Michael Stephens, a research fellow for the Middle East at London's RUSI think tank said, although he cautioned that the sentence had yet to be passed.

The outspoken Islamist cleric has been a thorn in the side of the ruling family for decades. In the 1990s, he criticized Saudi Arabia’s decision to allow the U.S. military into the country, was embraced by al Qaeda founder Osama bin Laden, and was imprisoned for opposing the government.

Al-Awda publicly and emphatically rejected bin Laden and al Qaeda, and has become one of the kingdom’s most popular clerics with millions of followers on Twitter. Then came the pro-democracy Arab uprisings of 2011 and al-Awda began advocating for greater democracy and social tolerance in the kingdom, according to Human Rights Watch.

Last year, the office for the U.N. high commissioner for human rights described al-Awda as “an influential religious figure who has urged greater respect for human rights within Sharia," referring to Islamic law.

“He was always very critical of how the regime plays up its Islamic credentials but they don’t live what they preach,” said Carool Kersten, an associate professor in the study of Islam and the Muslim world at King’s College London.

“His solution is another variant of an Islamic political system with a form of Sharia."

Al-Awda was sympathetic to the demands on the street and with a large following on social media, he became a real concern for the regime, Kersten added.

But it was when the youthful Salman rose to power that the gloves really came off, he said.

The murder of Washington Post journalist Jamal Khashoggi in the Saudi consulate in Istanbul in October sent ripples of revulsion throughout the world, endangering the crown prince's efforts to rebrand the country as modern and moderate.

Ever since rising to prominence after his father became king in 2015, the crown prince has pushed a sweeping rebrand of the country, promoting "moderate Islam" in a nation that for years has exported a strict and austere version of the religion.

President Donald Trump and Jared Kushner, his son-in-law and senior adviser, have embraced the crown prince as a close and crucial partner in the administration's Middle East strategy. Trump went to Saudi Arabia in his first foreign trip as president.

In an apparent attempt to transform the way the world sees the Gulf kingdom, Salman has instituted a series of social reforms such as allowing women to drive and approving movie theaters. But he has also overseen the arrests of critics and those who want political reforms alongside cultural changes.

In November 2017, the government rounded up dozens of members of the country's royal and business elite. Billed as part of a war on corruption, which is rampant in the kingdom, the move has also been widely seen as helping the prince tighten his grip on power.

In September 2017, al-Awda was arrested at his home and placed in solitary confinement. Last year, he was charged with 37 counts including affiliation with the Muslim Brotherhood, a political Islamist group founded in Egypt, that Saudi Arabia has designated a terrorist organization, according to Amnesty International.

Salman has jumped on the critical rhetoric around political Islam and painted al-Awda with the same brush, according to Kersten.

Politically, al-Awda was also seen as not supportive enough of the country’s sharp break with Qatar, with which Saudi Arabia cut off ties in 2017 and accused of supporting terrorism and archrival Iran.

According to Human Rights Watch, the first charge accuses al-Awda of “corrupting the land by repeatedly endeavoring to shake the structure of the nation and bring about civil strife; inflaming society against the rulers and stirring up unrest.”