BAGHDAD - Islamic State militants have kidnapped six members of Iraq's security forces and threatened to kill them in three days unless the government releases Sunni Muslim female prisoners, the group said on Saturday.In a video posted by the group's Amaq news agency, six men with visible injuries on their faces appear sitting on the floor with two masked gunmen, pointing assault rifles at them, standing behind. Islamic State's black banner hangs in the background.Iraq's military spokesman could not be immediately reached for comment.In the video, the men identify themselves as members of Iraq's police or the Popular Mobilisation Forces, an umbrella grouping of mostly Shi'ite Iran-backed militias that fought with government forces against Islamic State and nominally report to Prime Minister Haider al-Abadi."I implore the central government of Haider al-Abadi and the Anbar provincial government, we are now with the Islamic State, and we have three days. If the demand to release Sunni women from prisons is not met, we will all be killed," said one of the hostages.Abadi declared final victory over the hardline Sunni militants in December but the group still operates from pockets along the border with Syria and has continued to carry out ambushes, assassinations and bombings across Iraq.There has been an uptick in attacks by the group in recent weeks, especially on a highway connecting the capital Baghdad with the country's north where Amaq said the men in the video had been taken."We give the Rafidi government three days to release all Sunni detainees from prisons in exchange for releasing these apostates, or else their fate will be that of their predecessors," said one of the gunmen, using a slur for Shi'ites regularly employed by Islamic State.