A "human rights catastrophe" took place in southern Yemen during fighting between government forces and militants linked to the al-Qaeda terrorist network in 2011 and 2012, Amnesty International said in a report Tuesday, dpa reported.
The report, published in London, relates to fighting in the southern province of Abyan, where it said a "tragedy" took place as forces vied for control of the region.
In June Yemeni government forces and allied tribal fighters recaptured a string of towns in Abyan and neighbouring Shabwa province from the Ansar al-Sharia militia, which had held them since mid-2011.
Amnesty called on the Yemeni government to make sure that a commission of inquiry announced in September covered the "truly shocking abuses" committed.
"The tragedy of Abyan will haunt Yemen for decades to come unless those responsible are held to account and victims and their families receive reparations," said Amnesty spokesman Philip Luther.
Ansar al-Sharia (Partisans of Islamic Law) attacked government forces and officials, looted banks and seized ammunition, heavy weapons and other military equipment from abandoned Yemeni military and police stations, said the report.
Amnesty said it had evidence of abuse, including summary executions and amputations, carried out by members of the Islamist group.
It was responsible for widespread and disturbing human rights abuses, including via "religious courts," which frequently imposed cruel, inhuman and degrading punishments.
However, Amnesty also accused the Yemeni government of failing to "protect civilians" in the conflict, and using "inappropriate battlefield weapons" during its efforts to oust the militants from the region.
The use of airstrikes, artillery and mortar attacks in residential areas resulted in the deaths of civilians, it said. At the same time, the report criticized the militants for basing themselves among the population and "recklessly exposing civilians residents to harm."
"There are also reports that some of the airstrikes documented in this report may have been carried out by US drones, which appear to have been active during the conflict," the report added.
An estimated 250,000 people were displaced by the fighting, and there remains a danger that the Ansar al-Sharia could re-emerge, it concluded.