A prominent surgeon in Gaza has died in an Israeli prison after being held for more than four months, according to Palestinian prisoners’ groups, which decried his death as part of a “systematic targeting” of health care workers. Dr. Adnan Al-Bursh, head of orthopedics at Al-Shifa Hospital in Gaza City, was declared dead by Israeli prison authorities on April 19, according to a joint statement Thursday from the Palestinian Prisoners’ Society and the Commission of Detainees’ Affairs. Al-Bursh was arrested along with 10 other medical workers in December during the Israeli military ground invasion of the Jabalya refugee camp, CNN previously reported. He was taken away while treating patients in Al-Awda Hospital, according to the statement. His body has not yet been released by Israeli authorities. The prisoner associations blamed Israel for his death, saying it was part of a “systematic targeting process against physicians and the health care system in Gaza,” according to the statement. CNN has reached out to the Israel Defense Forces (IDF) for comment. The death of the 50-year-old was “heartbreaking news for everyone, for his family, the medical staff at Al-Shifa Hospital, and for Dr. Adnan’s patients,” the director of Al-Shifa Hospital, Dr. Marwan Abu Saada, told CNN. “This is the last thing we expected, and it’s difficult for the human soul to bear this news,” he said. “Dr. Adnan loved life, was cheerful, and was loved by everyone.” Abu Saada said he had earlier asked Israeli authorities about Al-Bursh’s detention but “didn’t receive any news.” Abu Saada was told that one of Al-Bursh’s fellow prisoners – who had since been released – said the surgeon had been tortured and was killed. CNN cannot independently verify the claim that Al-Bursh was tortured in detention. However, testimony from dozens of Palestinians who have been released by Israel in past months has alleged the widespread use of physical and psychological abuse of those detained by Israel during the war in Gaza. The IDF has previously said it treats all detainees in accordance with international law. An unpublished report compiled by the United Nations which CNN has obtained describes beatings, sleep deprivation, sexual abuse and threats of sexual violence against both men and women detained by the Israeli military. Earlier on Thursday, Israel released dozens of Gaza detainees via the Kerem Shalom crossing in southern Israel. The release included the return of the body of Ismail Khadr, a Palestinian man from Gaza, who had also recently died in Israeli custody, the prisoner associations said in the joint statement. The total number of Palestinian detainees who have died in Israeli custody since October 7 rose to 18, the statement said. Israel launched its military offensive in Gaza after the Hamas-led October 7 attacks when militants killed more than 1,200 people in southern Israel and took more than 200 people hostage. Israel’s military response has since sparked a humanitarian catastrophe in Gaza that has inflamed opinion globally. The seven-month bombardment of Gaza has killed more than 34,600 people, according to the Gaza health ministry. Half of the 2.2 million people in Gaza are on the brink of starvation and man-made famine is imminent, according to a scale used by United Nations agencies. Concerns are also heightened over an anticipated Israeli military operation in southern Gaza’s Rafah, prompting renewed calls for a ceasefire. There has been fierce criticism of Israel’s actions in and around hospitals in Gaza, as medical groups and NGOs warn the health system in the territory is on the brink of collapse. Israel has defended its military raids at medical facilities in Gaza, alleging that Hamas fighters used hospitals to run military activities through a network of underground tunnels. Hamas and medical staff at various hospitals across Gaza deny the allegations, and Israel has been under significant international pressure to prove its claims. — CNN