BAGHDAD: At least seven Iraqi Catholics died Sunday when police stormed a Baghdad church where gunmen were holding dozens of parishioners hostage, threatening to kill them if Al-Qaeda prisoners were not released. The US military said between seven and 10 hostages and seven members of the Iraqi security forces, as well as five to seven attackers, were killed in the rescue operation. Witnesses reported seeing many bodies inside the church after the gunmen wearing suicide vests threw grenades or blew themselves up as Iraqi forces stormed the building. The insurgents laid siege to one of Baghdad's biggest churches as more than 100 parishioners attended Sunday mass in a central district near the heavily fortified Green Zone, home to embassies and the Iraqi government. US military officials watched the rescue operation from cameras in hovering helicopters. Lt. Col. Eric Bloom, a US military spokesman in Baghdad, said three militants detonated suicide vests as Iraq forces entered the church. He said a total of 120 hostages were held by the assailants, adding that 30 people were wounded. Col. Kadhim Basheer Saleh, an Iraqi Civil Defense spokesman, said 15 civilians, four policemen and eight attackers were killed. Al-Qaeda's Iraqi affiliate, the Islamic State of Iraq, claimed responsibility for the attack. A federal police source said the attackers demanded the release of Al-Qaeda prisoners, including the widow of Abu Omar Al-Baghdadi, the former head of the Islamic State of Iraq, who was killed in April. In a separate call to al-Baghdadiya television station, a man who claimed to be one of the attackers said the group also wanted Al-Qaeda prisoners released in Egypt. Some police sources said they believed the initial target was the nearby Iraqi stock exchange, a bourse that lists a couple dozen local companies.