In a strongly-worded rejoinder to the lawyers on Thursday, the Shin Bet stated that it was aware of a deliberate and concerted effort to besmirch the organization and disrupt its operational activities.
The suspects, who have been held in administrative detention (detention without trial) since early November, were allowed to meet with their lawyers for the first time on Wednesday night.
Addressing a press conference on Thursday, the attorneys said that the descriptions of torture they had been given by their clients resembled the testimonies of Palestinians interrogated by the Shin Bet.
"The minor I met with was not the same person I knew previously," said Adi Kedar of the Honenu organization, who is representing one of the detainees.
"He has been deprived of sleep and they tied his arms behind his back and pulled on them until he vomited."
Itamar Ben Gvir, representing another of the detainees, said: "As far as we know there has not been any link made to Duma. They gave statements about crimes against property."
The Shin Bet, in its long and unusual statement, said that key activists in a terror group had been detained for investigation in light of the security threat they posed and the need to prevent them from carrying out further terror attacks.
The detainees, it added, were being interrogated intensively due to the suspicions against them.
The Association for Civil Rights in Israel said that the statements made by the lawyers raised serious doubt regarding the use of illegal interrogation methods, such as the use of physical force and the deprivation of sleep for long periods.
"Such methods have been rejected by the High Court as torture," the association said in a statement. "We call on whoever in the Justice Ministry is responsible for investigating complaints against the Shin Bet to open an immediate investigation into the latest complaints.
Raz Nizri, the deputy attorney general for criminal law, told a Knesset committee on Monday that extraordinary measures have been used in questioning the suspects.
Speaking to a session of the Knesset Constitution, Law and Justice Committee debating the extension of a temporary order preventing security suspects from meeting with their lawyers, said the measures were approved by Attorney General Yehuda Weinstein and had judicial oversight.
In a conversation with Haaretz, Nizri said the extraordinary measures included waiting more than 48 hours before bringing suspects before a judge and the extension of their detention period in absentia.
On Sunday, the High Court of Justice authorized the Shin Bet to continue preventing three suspects from meeting with their lawyers.
Want to enjoy 'Zen' reading - with no ads and just the article? Subscribe todaySubscribe now