The campaigners have released new footage, showing a handcuffed child with his pants down.
Activists claimed the minor was beaten and sexually harassed by Saudi-backed forces.
He was left unconscious with his hands tied behind his back, and was found lying in a street by residents in the village of Sanabis, outside of Manama, they said.
Press TV was not able to verify the authenticity of the footage.
Bahrain has been in a revolution since anti-government protests broke out in February 2011.
Forces loyal to the Al Khalifa ruling family have since killed scores of protesters and arrested thousands more.
MRS/JR/IS
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