Jerusalem, Nov 16 : A top Israeli official said he was sure that "more and more material" will be shared from the military's search operation at Gaza's Al-Shifa Hospital, where the Jewish nation believes that the Hamas militant group operates a subterranean network of tunnels. Justifying the military operation at the enclave's largest hospital, Mark Regev, a senior adviser to Israeli Prime Minister Benjamin Netanyahu, told the BBC on Wednesday night that "international law specifically says that the minute your enemy uses a humanitarian site like a hospital for its military machine then you can target that site". "It doesn't mean you do so lightly or irresponsibly but under international law it loses its immunity," he added. Regev's remarks came as Israeli special forces backed by additional troops conducted the "precise and targeted operation" inside the hospital against Hamas terror infrastructure at the site. The operation lasted until Wednesday evening, with the Israel Defense Forces (IDF) finding weapons and Hamas assets inside the premises, while it also interrogated people. At least five Hamas gunmen were killed by troops during a gun battle outside the hospital, The Times of Israel reported, adding that no soldiers were injured. Addressing the media, IDF spokeperson Daniel Hagari said on Wednesday night that the operation lasted some 18 hours. He said that the IDF searched the hospital premises extensively and did not rule out the possibility of getting Hamas terroists who are hiding in some areas in the facility. The Israeli military has repeatedly alleged that Palestinian armed groups operate a military compound within and underneath the Shifa Hospital. The hospital's management and the Palestinian Ministry of Health in Gaza have strongly denied these allegations and have called for an independent investigation. Presently, it remains unclear what or who remains in the complex following the Israli operation. Meanwhile, the Israeli army stressed that the military was "not overrunning" the hospital, asserting troops were conducting a "focused" operation "in a defined area" of the hospital. Though Israel believes some of the 240 hostages captured by Gaza terrorists were housed at the hospital at one time, there is no indication of hostages currently being held there. However, the IDF believes the operation may bring intelligence information on the captives. Responding to the operation, senior Hamas member Bassem Naim called it "ridiculous and worthless" and said he could not rule out that the Israeli military "brought weapons and put them in the Al-Shifa complex", the BBC reported. He said Israel's goal is to "pressure" hospitals and medical centres and to displace Gaza's population, adding that 25 hospitals in the territory are now out of service through "bombing, siege and destruction". Hamas has repeatedly denied Israeli claims that it operates from within the hospital. The Health Ministry in Gaza said that before the military raid in Al-Shifa, bombardments hit the hospital and damaged parts of it, including the specialised surgeries department, coronary care division and a warehouse. "After the troops entered, patients, staff and IDPs were reporteldy relocated within the compound," it said. The Ministry also claimed that on Wednesday, 179 bodies held at Al Shifa, which could not be evacuated or properly maintained, were buried in a mass grave inside the compound. /IANS