A rights group says 10 people, including 2 U.S.-Saudi dual nationals, have been detained in a new "vicious crackdown" in Saudi Arabia.

Those reportedly arrested are mostly journalists and authors, and many are linked to female activists already on trial.

It is the first purported "campaign of arbitrary" arrests in the kingdom targeting perceived critics of Crown Prince Mohammed bin Salman since the murder of journalist Jamal Khashoggi.

Saudi Arabia has reportedly detained at least 10 people, including two U.S. dual nationals, in what one human rights groups called on Friday a "new campaign of arbitrary arrests" aimed at advocates for free speech and human rights. "We reject this vicious crackdown and call for the immediate release of all prisoners of conscience," the Prisoners of Conscience organization said in a tweet on Friday.

The Associated Press also reported a new round of arrests, citing an anonymous source "with knowledge of the apprehensions," but put the number of new detainees at eight, also including two American dual nationals.

Rights groups are not permitted to operate inside the conservative Islamic kingdom, but there are a couple that have members who work covertly, at great risk to their safety, to reveal such information, including the Prisoners of Conscience. As the activists work anonymously, the information about the new arrests -- like most proceedings in Saudi Arabia's secretive justice system -- could not be independently confirmed.

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It marks the first sweep of arrests to target individuals perceived as critics of Crown Prince Mohammed bin Salman since the killing of writer Jamal Khashoggi in the Saudi Consulate in Istanbul in October. The arrests come despite global outcry over Khashoggi's grisly killing by Saudi agents in an operation directed by former top aides to the crown prince, and which the CIA has concluded the crown prince himself very likely ordered.

Who was detained

Both Prisoners of Conscience and the AP reported that U.S.-Saudi dual nationals Bader Al-Ibrahim, a writer and physician, and Salah al-Haidar, whose mother is prominent women's rights activist Aziza al-Yousef, were among those arrested.

Al-Haidar has a family home in Vienna, Virginia, but lives with his wife and child in Saudi Arabia.

All of those reportedly taken into custody have voiced support for increased women's rights in the kingdom or have close ties to other people already jailed. Most of those swept up in the purported crackdown were journalists or authors, including Moqbal Saqqar, a novelist who wrote a book highlighting the challenges women face in Saudi Arabia, where the government implements a strict form of Islamic rule.

The arrested individuals, nearly all of whom were detained on Thursday, are not seen as front-line activists but rather people who have quietly supported greater social reforms, and most have ties to a group of women's rights activists currently on trial.

Khadijah al-Harbi, a feminist writer who is currently pregnant, and her husband Thumar al-Marzouqi, also a writer, were among those detained, both the rights group and the AP said.

Nearly all of those detained Thursday were taken from their homes in the capital, Riyadh. One individual was arrested in the eastern city of Dammam, according to the person with knowledge of the arrests, who spoke to the AP on condition of anonymity for fear of retribution.

The others arrested, according to Prisoners of Conscience, were journalist Yazid Alfaifi and authors Mohamed El Sadek, Abdullah al-Duhailan, Fahad Abakhail and Anas al-Mazrou'a.

Women already on trial

Meanwhile, the siblings of Loujain al-Hathloul, a female activist detained since May, stated on Twitter this week that they are being pressured to remain silent about her arrest and her claims of torture. The siblings live outside Saudi Arabia, but their father who resides in Saudi Arabia was previously briefly detained after tweeting about his daughter's imprisonment.

Al-Hathloul and Aziza al-Yousef are among nearly a dozen women on trial for charges related to their activism, which included campaigning for the right to drive before the ban was lifted last year and calling for an end to guardianship laws that give men final say over a woman's right to marry or travel abroad.

Al-Yousef, a grandmother and former university professor, was released from prison last week along with two other women. Al-Hathloul and at least 10 other women activists remain imprisoned.

The women -- some of whom have been held in solitary confinement for months -- have told the court they were abused during interrogations, including being waterboarded, caned, electrocuted, sexually assaulted and threatened with rape and death.