At least some of the clandestine missions were carried out by members of the same team that killed and dismembered Mr. Khashoggi in Istanbul in October, suggesting that his killing was a particularly egregious part of a wider campaign to silence Saudi dissidents, according to the officials and associates of some of the Saudi victims.

Members of the team that killed Mr. Khashoggi, which American officials called the Saudi Rapid Intervention Group, were involved in at least a dozen operations starting in 2017, the officials said.

Some of the operations involved forcibly repatriating Saudis from other Arab countries and detaining and abusing prisoners in palaces belonging to the crown prince and his father, King Salman, the officials and associates said.

One of the Saudis detained by the group, a university lecturer in linguistics who wrote a blog about women in Saudi Arabia, tried to kill herself last year after being subjected to psychological torture, according to American intelligence reports and others briefed on her situation.