BEIRUT, Lebanon — Brushing back pressure from Washington, Crown Prince Mohammed bin Salman of Saudi Arabia escalated his crackdown on even the mildest forms of dissent with the arrests this week of at least nine intellectuals, journalists, activists and their family members, according to rights groups and a Saudi associate of the detainees.

Among those held are two dual Saudi-American citizens and two women — one of them pregnant, the groups said. Many of the detainees are suspected of having complained to Western journalists and rights groups about the treatment of imprisoned women’s activists, according to a Saudi national briefed on the case who spoke on the condition of anonymity in order to discuss confidential information.

The arrests come as Prince Mohammed, the 33-year-old de facto ruler of the kingdom, is under intense scrutiny over the killing last fall of the dissident Jamal Khashoggi, a Virginia resident and Washington Post columnist who was ambushed and dismembered by Saudi agents in Istanbul. American intelligence agencies have concluded that Prince Mohammed ordered the killing.

In the aftermath, a chorus of American lawmakers from both parties have urged the crown prince to loosen his iron-fisted grip by releasing some of the nonviolent activists. Many lawmakers have focused attention on a small group jailed for campaigning for reforms to the kingdom’s austere social code — including the right for women to drive, which Prince Mohammed has granted.