"Nothing can justify caging people and intentionally putting them in harm's way, even if the purpose is to stop indiscriminate government attacks," said Nadim Houry with Human Rights Watch, CNN reports.
Videos posted to social media over the weekend show trucks transporting cages filled with up to eight men or women, the opposition Shaam News Network reported.
"Rebels ... have distributed 100 cages, with each cage containing approximately seven people and the plan is afoot to produce 1,000 cages to distribute ... in different parts of Douma city particularly in public places and markets that have been attacked in the past by the regime and Russian air-force," text in one of the videos says, according to the opposition network.
Read alsoReuters: Al Qaeda chief urges militant unity against Russia in SyriaCNN also found the videos online too, but cannot independently verify their authenticity.
The move came in the days after government attacks on a marketplace in Douma last week killed dozens and wounded hundreds.
The area, only 26 km east of Damascus, has been heavily shelled the past three weeks.
Read alsoAP: Activists say suspected Russian jets hit Syria's PalmyraHuman Rights Watch said Assad's forces have also used this tactics earlier.
There was no immediate response from the regime and no word from the opposition on whether the tactic had accomplished its goals.
The Army of Islam is one of the most powerful rebel factions operating near Damascus and is not backed by the United States.