Amnesty International released a report Tuesday detailing "a raft of gross and deeply disturbing" incidents that occurred in the governate of Abyan after al-Qaida affiliate Ansar al-Sharia took over the region.
During Ansar al-Sharia's rule, "religious courts" imposed cruel, inhuman and degrading punishments that included summary killings, amputations and floggings, Amnesty International said.
One young man suspected of theft had his hand amputated and the hand was suspended by a rope in the town's market for all to see, the group said.
"Abyan experienced a human rights catastrophe as Ansar al-Sharia and government forces vied for control of the region during 2011 and the first half of 2012," said Philip Luther, Amnesty International's director for the Middle East and North Africa.
Yemen's army finally drove Ansar al-Sharia out of Abyan in June.
The London-based organization has called for an "impartial, thorough and independent" investigation saying those responsible must be held to account.