ISTANBUL — A second senior official with Amnesty International, the leading human rights watchdog, has been detained in Turkey in the space of a month.

Idil Eser, the director of Amnesty’s Turkey office, was detained on Wednesday along with at least 10 others after a raid on a digital security workshop at a hotel on Buyukada, one of the Princes Islands near Istanbul.

The detainees included seven other activists from local rights groups; two foreign trainers; and the hotel owner, who was later released, Amnesty said. After the detainees were held without access to lawyers for more than a day, officials announced that they were being investigated on suspicion of connection to a terrorist group.

Ms. Eser’s detention follows that of the chairman of Amnesty’s Turkey chapter, Taner Kilic. Mr. Kilic was arrested last month on charges of having a connection to the Islamic group that is accused of spearheading the failed coup in Turkey last year.