Mr. Abdulrahman, who uses a nom de guerre for security, used shock tactics in previous videos intended to draw the world’s attention to government airstrikes that have killed scores of people in the area. In February, he staged a propaganda message that self-consciously echoed an Islamic State video in which a caged Jordanian pilot, in an orange jumpsuit, was burned alive.

In that clip, the activist appealed for help from the outside world by speaking to the camera about the strikes while standing in front of a cage filled with neighborhood children dressed in orange. After waving a torch, Mr. Abdulrahman asked why the killing of the pilot had prompted global condemnation while the deaths of children in Douma had passed almost unremarked on.

The new propaganda videos featured interviews with hostages in the cages who demanded that the Assad government stop the bombardment of the area and negotiate their release. It was very unlikely that, given their situation, any of those interviewed by the activists or local journalists from channels that support the rebellion felt they could speak freely.

“I hope the regime and the Russian jets stop the bombardment,” said one female prisoner identified as being originally from the president’s hometown. While the male prisoners appeared to be members of the Alawite sect, an offshoot of Shiite Islam, Joshua Landis, a Syria expert at the University of Oklahoma, suggested that some of the women appeared to be Sunni Muslims.

The Army of Islam, a group with financial backing from Saudi Arabia, is led by Zahran Alloush, a Sunni commander who seemed to back away from sectarian anti-Alawite statements in an interview with an American journalist, Roy Gutman, in May.