TRIPOLI — Misrata militias are carrying out revenge attacks on the displaced residents of the nearby town of Tawargha, a stronghold of Moamer Kadhafi loyalists during Libya's eight-month conflict, a rights group said on Sunday.

New York-based Human Rights Watch said in a statement it had received credible reports of Misrata militias shooting unarmed Tawarghans, and of arbitrary arrests and beatings of detainees, in a few cases leading to death.

"Militias from the city of Misrata are terrorising the displaced residents of ... Tawargha, accusing them of having committed atrocities with Kadhafi forces in Misrata," HRW said, adding its conclusion was based on the testimonies of dozens of people across the country.

The rights group also documented widespread looting and torching of houses in Tawargha as recently as last Wednesday, and quoted Misrata militiamen arguing that its residents should never be allowed to return after "what they did in Misrata."

The rights watchdog urged the National Transitional Council to bring the more than 100 armed groups from Misrata under a central command and hold them to account for their actions.

Tawargha served as a base for attacks on Misrata, Libya's third city which suffered a five-month siege by pro-Kadhafi forces.

Tawargha residents scattered in August after the Misrata militia punched their way out of the siege and began an advance on Tripoli, which they overran on August 23.

The authorities and inhabitants of Misrata widely accuse Tawargha's residents of having committed serious crimes alongside Kadhafi's forces, including murder and rape, HRW said.

"Revenge against the people from Tawargha, whatever the accusations against them, undermines the goal of the Libyan revolution," HRW's Middle East and North Africa director Sarah Leah Whitson said in statement.

"In the new Libya, Tawarghans accused of wrongdoing should be prosecuted based on the law, not subject to vigilante justice," she added.

Disbanding Libya's numerous militias or integrating them into a professional army, and reconciling with the residents of former Kadhafi strongholds like Sirte, Bani Walid and Tawargha, are among the key challenges facing the new regime.