BEIRUT — As Saudi Arabia prepares to virtually host the annual Group of 20 summit meeting in Riyadh on Saturday, human rights groups and the families of jailed Saudi dissidents are mounting an unusually vigorous campaign aimed at highlighting the kingdom's abuses and the plight of political detainees.

Saudi Arabia announced in September that the annual, typically lavish gathering of the world’s largest economies would be held online because of the coronavirus pandemic — a setback for the modernizing country, which had envisioned the event as a chance to showcase its successes.

But along with the challenge of hosting a toned-down virtual G-20 summit, Riyadh is facing a wave of calls urging world leaders to boycott or downgrade their attendance if demands for the release of Saudi female activists and other conditions are not met.

The calls — from Saudi and international human rights groups, and also U.S. and European lawmakers — have confronted the kingdom with a barrage of criticism unlike any since the killing of journalist and Washington Post contributor Jamal Khashoggi by Saudi agents two years ago, while forcing normally circumspect Saudi leaders to publicly defend their policies.

“Saudi Arabia seeks to have a leading role, but the leaders from other countries have a moral obligation to ask Saudi Arabia to improve its record on human rights,” said Alia al-Hathloul, the sister of jailed women’s rights activist Loujain al-Hathloul, whose plight has become a rallying cry for the kingdom’s critics and who recently renewed a hunger strike to protest her detention. United Nations experts have called for her release, warning that her health is deteriorating.

Saudi Arabia is the first ­Arab-majority nation to assume the year-long presidency of the G-20, which is made up of 19 countries and the European Union. The designation was a diplomatic coup for Saudi’s de facto leader, Crown Prince Mohammed bin Salman, who has quickly risen to global prominence with an agenda to overhaul the oil-rich kingdom’s economy and conservative society.

But while Saudi organizers set the two-day summit’s official theme as “Realizing Opportunities of the 21st Century for All,” human rights groups sought to amplify what they said is Mohammed’s darker legacy: the silencing, harassment, arbitrary jailing, disappearance and torture of his opponents.

Although pressure in some circles has been building, no G-20 members have announced plans to withdraw from the summit.

Even so, the criticism has prompted an unusual public airing of grievances between the kingdom’s leaders and its opponents. The crown prince, in a lengthy and rare public statement earlier this month, defended his stewardship of the Saudi economy while touting progress on promoting women’s rights. On Wednesday, the Saudi ambassador to the United States, Princess Reema bint Bandar, also offered a full-throated defense of Saudi changes and lashed out at the kingdom’s critics.

Saudi Arabia is “too often misunderstood, our remarkable progress, reform and change, too often overlooked,” she said in a speech to the National Council on U.S.-Arab Relations. “Some critics still cling to outdated, outmoded, completely obsolete views of the kingdom. When we are challenged on human rights, we need to better explain that change doesn’t happen all at once.”

Saudi and international rights activists, meanwhile, have argued that a years-long crackdown on dissent by Mohammed is largely unprecedented in the kingdom’s recent history.

“The G-20 presidency has conferred an undeserved mark of international prestige on the government of Crown Prince Mohammed bin Salman,” Michael Page, deputy Middle East director of the New York-based Human Rights Watch, said in a statement. “Instead of signaling its concern for Saudi Arabia’s serious abuses, the G-20 is bolstering the Saudi government’s well-funded publicity efforts to portray the country as ‘reforming’ despite a significant increase in repression since 2017.”

As one retort, Saudi dissident human rights groups have organized an “Alt G-20” to virtually coincide with the Riyadh summit and protest the crown prince’s crushing of dissent.

In October, 45 U.S. lawmakers sent a letter to Secretary of State Mike Pompeo urging Washington to boycott the summit unless Saudi Arabia addressed a litany of human rights concerns. The list included accountability for the 2018 murder of Khashoggi, which the CIA concluded Mohammed had ordered, the release of jailed female activists and an end to Riyadh’s military campaigns in war-torn Yemen.

Pompeo will be in Riyadh for the summit and to meet with the crown prince, who has denied involvement in Khashoggi’s killing. The White House confirmed Friday that President Trump, who has forged close ties with Mohammed, will virtually attend, as the U.S. leader continues to contest his defeat in this month’s presidential election.

The E.U. Parliament in October similarly passed a nonbinding resolution urging the E.U. to downgrade its delegation to “avoid legitimizing impunity for human rights violations and ongoing illegal and arbitrary detentions in Saudi Arabia.” The resolution, passed on the second anniversary of Khashoggi’s murder in the Saudi Consulate in Istanbul, also highlighted the cases of incarcerated political dissidents, such as blogger Raif Badawi, and the detention of Ethiopian migrants in Saudi prisons.

Organizers of the Riyadh summit did not provide a list of who would be representing each of the G-20 members and countries invited. German Chancellor Angela Merkel, Chinese President Xi Jinping and Russian President Vladimir Putin, among other leaders, are expected to speak at the summit, according to sources cited by Agence France-Presse.

Without the one-on-one interactions typical of a G-20 summit, Alia al-Hathloul predicted that it might be harder for world leaders virtually attending to discuss sensitive matters such as her sister’s case. Even so, she expected that “there are many opportunities” for such issues to be raised at the summit, in addition to follow-up meetings and calls. Loujain, her sister, was among a group of Saudi feminists arrested two years ago after advocating for reforms including the right to drive and the repeal of male “guardianship” laws.

Activists similarly targeted various events leading up to the G-20 summit. Last month, London Mayor Sadiq Khan joined the mayors of other major cities, including New York and Los Angeles, in boycotting a G-20-linked event, called the Urban 20 summit, in a show of support for Saudi political prisoners.

Fahim reported from Istanbul.