Last month, the national assembly ordered force to be used if needed to arrest those responsible for kidnapping and shooting Shaaban Omran, who succumbed to his wounds shortly after the authorities brokered his release from Bani Walid.
The September 25 order by the General National Congress has been followed by a gradual build-up of army and militia forces around the oasis town, a final bastion of Kadhafi loyalists in the 2011 conflict.
“It is worrying that what essentially should be a law-enforcement operation to arrest suspects looks increasingly like a siege of a city and a military operation,” said Amnesty deputy director for the Middle East and North Africa, Hassiba Hadj Sahraoui.
Residents report that vehicles carrying petrol, water, food and medical supplies have been turned back at a checkpoint about 80 kilometres (50 miles) away from Bani Walid on the main road from Tripoli, the watchdog said.
Omran was a native of Misrata, and his death last month stoked tensions between Bani Walid and Misrata, neighbouring but historically rival cities that fought on opposite sides of last year’s war.
The authorities have also called for the release of other detainees held in Bani Walid and set a 10-day deadline, which expires on Friday.
“At least four other Misratans are believed to be held by armed militias in Bani Walid,” Amnesty International said.
Bani Walid was one of the last cities to fall to anti-Kadhafi rebels. Many fighters from Misrata and other areas feel that the town was never truly liberated and that it shelters remnants of the old regime and criminal elements.
Sahraoui said “Libyan authorities should ensure that maximum restraint is exercised in any use of force, which should be proportionate to the purported objective of arresting suspects.”
On Tuesday, one person was killed and five wounded in clashes near Bani Walid, said local leaders, who accused Misrata militiamen of trying to enter the city.
In the absence of a robust army, the authorities typically mobilise to hot spots brigades made up of former rebel, but some groups act of their own accord.
Amnesty noted that hundreds of Bani Walid residents have also been arrested by militias and remain held without charge in detention centres across Libya, including in Misrata.
Many of them have been tortured, said the organisation.
Sahraoui urged the authorities to put an “immediate end to ongoing abductions of individuals without warrant by armed militias and close all unofficial detention facilities.”