Armed groups, some linked with prominent Libyan commander Khalifa Haftar, are preventing thousands of displaced families from returning to the eastern city of Benghazi, Human Rights Watch (HRW) said in a report published on Thursday.
Groups affiliated to Haftar's Libyan National Army (LNA) have seized property from displaced families, and tortured, abducted or arrested people who tried to resist, HRW said it had heard from their relatives.
The LNA did not immediately respond to a request for comment. Last month, Haftar issued a statement denouncing attacks on private property and calling for LNA forces to help the displaced return.
The LNA prevailed last year in a long military campaign against Islamists and other opponents of Haftar for control of Benghazi. Haftar has emerged as the dominant figure in eastern Libya and is a likely presidential candidate in elections that the United Nations says it wants to hold by the end of the year.
The war in Benghazi was part of a wider conflict that developed in Libya after a 2011 uprising ended more than four decades of rule by Muammar Gaddafi, and has seen tens of thousands of people displaced across the country.
Since the start of Haftar's "Dignity Operation" in May 2014, around 13,000 families have fled Benghazi, and at least 3,700 families are being blocked from returning, HRW said, citing local activists.
The rights group called on Haftar to end the attacks against civilians. "Senior LNA commanders who have stood by since 2014 while their forces torture and disappear people and plunder their property can and should be held to account by local or international courts," Eric Goldstein, HRW's deputy Middle East and North Africa director, said in a statement.
Some displaced families interviewed by HRW said they were unable to return to Benghazi due to threats even though none of their relatives had fought against the LNA. Most said their families had been targeted on the pretext that they or their relatives were linked to Islamic State.
HRW said five relatives of interviewees were among 36 victims found in the town of Al-Abyar in October, the worst in a series of such incidents.
"We are now seeing a very frightening acceleration of extra-judicial killing, or people who appear to be prisoners, appear to be alive when they are caught, and the family loses track of them and then they turn up dead," HRW senior Libya researcher Hanan Salah said by phone.
"We are continuously documenting the exact same cases of people who disappear at night, whose parents are then afraid to go look for them, and who turn up dead in a dump."
In some cases, the fact that families long resident in Benghazi had origins in western Libya and particularly in Misrata, a bastion of opposition to Haftar, was used against them, said Salah.
"This is going to make any future settlement very difficult, and future reconciliation or accountability very, very difficult," she said.