An international rights group has urged Libyan strongman's self-styled army to lift its siege inside an eastern Mediterranean city where civilians have been trapped.

Human Rights Watch said on Friday that over the past two weeks, Gen. Khalifa Hifter's forces have been carrying out arbitrary arrests in Darna and laying siege on its Old City. It's unclear how many civilians are trapped in the Old City.

Hifter's Libyan National Army, with the backing of Egypt, has waged a campaign to take control of Darna since last May from the city's Islamic militias known as the Shura Council of Darna Mujahedeen, until defeat.

Sarah Leah Whitson, Mideast chief at Human Rights Watch, urged Hifter's army to "end the nightmare for any trapped civilians and account for the people in its custody."