An activist group on Sunday accused Israeli security forces of torturing a Palestinian arrested on suspicion of leading a West Bank bomb attack that killed an Israeli teenager. Israeli police and the Shin Bet domestic security agency late on Saturday said they had arrested three members of the Popular Front for the Liberation of Palestine weeks ago for the August 23 bombing. The explosion near a spring close to the Jewish settlement of Dolev, north-east of Ramallah in the occupied West Bank, killed Rina Shnerb, 17, and wounded her father and brother. Shin Bet identified the cell leader as Samer Al Arbeed. It said the group involved "was preparing other attacks when the arrests occurred, notably gun attacks and a kidnapping". On Sunday, Palestinian prisoner support group Addameer said that Arbeed was taken to hospital after suffering a "serious health deterioration due to torture and ill-treatment during interrogations." Addameer said Mr Al Arbeed, 44, was "harshly beaten" by the Israeli police who arrested him. Shin Bet investigators "continued using torture and ill-treatment", the activist group said. Mr Al Arbeed suffered broken ribs and "severe kidney failure", his lawyer told Addameer. Police refused to comment on the nature of his arrest, while Shin Bet claimed that during his interrogation he said "he did not feel well". "In accordance with procedures, he was transferred to medical examination and care at a hospital," the security agency said. Shin Bet refused to provide further details because "the investigation of the terror cell was still ongoing". Palestinian Health Minister Mai Al Kaila appealed to international organisations to "intervene to save the prisoner". The Palestinian Prisoners Club called the incident "a crime authorised by the judiciary". The bombing attack perplexed Israeli security agencies because it involved a hidden bomb, a tactic rarely used by Palestinian militants in the West Bank. In the West Bank, where 7,000 Israeli settlers live among over 2.5 Palestinians, Palestinian attackers often strike Israeli settlers and soldiers by stabbing, ramming with cars or drive-by shootings. Israeli Prime Minister Benjamin Netanyahu on August 26 ordered hundreds of new settler homes to be built near the site of the bomb attack.