Both Human Rights Watch and Amnesty International said in new tallies released on Wednesday that the Saudi authorities had now arrested as many as 11 activists, more than double the number confirmed five days earlier.

Saudi prosecutors have not disclosed the names of those arrested or any charges filed against them, but a government statement has accused them of “suspicious contact with foreign parties” and of undermining “security and stability.”

Pro-government news outlets and social media accounts have called them “traitors,” with one account splattering the word in red across their faces, or as “agents of embassies,” suggesting they worked for foreign governments. One newspaper said they could face as much as 20 years in prison for treason.

News reports have identified some of those arrested. One of the best known, Loujain al-Hathloul, is in her late 20s; she was previously detained for more than 70 days in 2014 for trying to post an online video of herself driving into the kingdom from the United Arab Emirates. Others include a retired professor with five children and eight grandchildren; an assistant professor of linguistics who is also a blogger in English and the mother of four; a psychotherapist in her mid-60s; and a twentysomething nurse in Riyadh, the Saudi capital. One of a handful of men arrested is a lawyer who defended Ms. Hathloul when she was previously arrested.

Crown Prince Mohammed, 32, is unapologetically authoritarian, and his defenders argue that top-down authoritarianism is the only way to modernize the conservative kingdom, whether by gradually opening up more freedoms for women or by liberalizing the economy to attract foreign investment.

But the crown prince badly tarnished his image as an economic reformer when he ordered the arrests last fall of about 200 wealthy businessmen and officials, incarcerating them in a Ritz-Carlton Hotel and forcing many to surrender assets in exchange for their freedom. His supporters called it a crackdown on corruption. Critics — and investors — saw it as a shakedown.