Their captors forced them to film a video appeal to Duterte to accede to the militants ' demands or the hostages would be killed .
The men said they were part of a group of 20 who had been taken captive on 27 May while evacuating the city .
men 's captors forced them to film a video appeal to Duterte to accede to the militants ' demands or the hostages would be killed .
The men said they were part of a group of 20 who had been taken captive on 27 May while evacuating the city .