In a letter to military and civil leaders of Misurata, the rights group cited "ongoing torture and abuse in detention facilities" in and around Misurata, and continued arrests, torture and forced displacement of people from the nearby town of Tawergha.
The abuses, the rights group said in a release, appear so widespread and systematic they may amount to crimes against humanity.
"Our letter to Misurata authorities is a wake-up call," Sarah Leah Whitson, Middle East director at Human Rights Watch, said in the release. "Five months after the conflict with Gadhafi forces ended, militias from Misurata are still committing serious abuses -- crimes under Libyan and international law -- and the city's leaders can be held legally responsible for those acts by the ICC."
The group said forces loyal to ousted Libyan strongman Moammar Gadhafi, who was killed by rebel fighters after his capture last October, had committed war crimes against people in Misurata, but said those crimes do not justify abuses happening now.
The ICC has jurisdiction over war crimes and crimes against humanity committed in Libya since Feb. 15, 2011, the group said, and could prosecute military commanders and senior civilian officials for serious crimes.
Human Rights Watch noted a U.N. Commission of Inquiry had concluded March 2 militias from Misurata apparently had committed crimes against humanity.
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