BAGHDAD, Iraq (CNN) -- Five U.S. Marines were killed in Iraq on Wednesday during a firefight near the Syrian border in Ubaydi, the military said.Sixteen insurgents were also killed in the fighting, part of Operation Steel Curtain, a U.S.-Iraqi military offensive aimed at clearing insurgents out of towns in northwestern Iraq.The announcement brought the number of U.S. troops killed in the Iraq war to 2,079, according to U.S. military reports.Operation Steel Curtain was launched in Husayba on November 5 and forces have also been deployed into parts of the nearby city of Karabila.Husayba had become a command and control center for insurgents and foreign fighters, the military has said. News of the American casualties came as a prominent Sunni Muslim party called for an international investigation into allegations that detainees were being tortured in an Iraqi Ministry compound.The facility allegedly held more than 160 detainees -- some who showed signs of apparent torture.The Iraqi Islamic Party, which helped broker the deal that brought a national constitution to a national referendum in October, said Wednesday the detainees were mostly Sunnis and the human rights violations at the compound were part of a campaign to marginalize Sunnis ahead of another nationwide vote next month."The Islamic Party appeals to the U.N., Islamic Conference Organization, Arab League and human rights organizations all over the world to condemn the flagrant violations of human rights under the current government and demand them to launch an international investigation so that those involved would get just punishment," the party said in a statement."I have the full story of this shelter," said party secretary-general Tariq al-Hashimi. "I have all the documents about that." (Watch: Footage of abuse in similar cases in Iraq -- 3:04)"Nobody except the Sunni community are reporting missing people," al-Hashimi said. "I have a concrete knowledge about what I am talking about. I am sure those people being discovered in this shelter are exclusively Sunni people."He displayed a report with what he said were photographs of abuse victims and a CD that he said contained the information he planned to present to the United Nations and other international organizations. Prime Minister Ibrahim al-Jaafari said Tuesday the prisoners were found malnourished and possibly tortured by government security forces at a Baghdad lockup. He has launched an Iraqi-led investigation with U.S. assistance.Deputy Interior Minister Hussein Kamal has dismissed as "nonsense" allegations that a majority of detainees were Sunni."There are Turkomen from Tal Afar, there are Kurds, Arabs, Sunni and Shia," he told CNN.He also denied an allegation that the facility was run by the Badr organization -- the military arm of the Supreme Council of Iraqi Revolution in Iraq Shiite party."These are employees of the Ministry of Interior, not affiliated with one organization or another," he said.The U.S. military said they found the detainees Sunday when they entered a building controlled by the ministry while looking for a missing 15-year-old boy. The boy was not there, but the detainees were. Iraqi police said the building was run by "police commandos" who work for the Interior Ministry.In Iraq, police answer to the Interior Ministry, while the Iraqi military answers to the Ministry of Defense.While the U.S. military would not confirm the condition in which they found the detainees, Iraqi police said they had been tortured. Kamal confirmed that human rights abuses had taken place and that the facility was run by the Interior Ministry's Special Investigation Unit."I saw signs of physical abuse by brutal beating -- one or two of the detainees were paralyzed and had their skin peeled off various parts of the body," he told CNN Tuesday.Kamal said the building housed 161 detainees.Al-Hashimi said the presence of the facility was not entirely a surprise -- it was merely "the missing link" in what he said was a series of arrests of Sunnis that ended with either a missing person report or a body."When I talked to minister of the interior, I told him many times I have a list of missing detainees," he said. "He (Interior Minister Bayan Jabr) said I could go and check the prisons, and he ... told me about 4 or 5 official prisons.""I sent my staff to go and check the prisons," al-Hashimi said. "At the end of the day, I didn't discover those detainees. So it gave me the impression that there are hidden and secret camps in fact being again directed and managed by Ministry of Interior, but no one knows about them."Al-Hashimi called for Jabr's immediate replacement and said he feared there were more such facilities."I am sure that there are many other secret camps being used by Ministry of the Interior, and we have to move very quickly, make this survey and try to announce to the Iraqi people," he said."Whoever might have some sort of information about these secret camps should present it to a reliable source and try to gather this information and pass it to the American troops or whoever will now manage the file of this case."Other developmentsThe U.S. military reported that a Task Force Baghdad soldier died Wednesday from wounds sustained when a roadside bomb went off a day earlier northwest of Baghdad.Three U.S. soldiers died Tuesday when their patrol struck a roadside bomb northwest of Baghdad, the military said. The soldiers were assigned to Task Force Baghdad. Their names were withheld pending notification of relatives. The incident is under investigation, the military said. The deaths bring the number of U.S. troops killed in Iraq to 2,072.The U.S. military said it had captured a key leader of al Qaeda in Iraq. Ayadah Husayn Matar, known as the emir of Sada, was among suspected insurgents and foreign fighters captured earlier this month in a raid on a safe house. Matar, also known as Abu Ahmed, was responsible for all terrorist operations in Sada. The Pentagon has acknowledged U.S. troops used white phosphorous as a weapon against insurgents in Falluja last year. But they denied allegations in an Italian television news report that the spontaneously flammable material had been used against civilians. (Full story)CNN's Enes Dulami, Cal Perry and Mohammed Tawfeeq contributed to this report.