- Group alleges Hamas forces carried out extrajudicial killings of at least 23 Palestinians
- Some killings were carried out before onlookers, including children, Amnesty says
- Brother of victim: "His body was as if you'd put it in a bag and smashed it"
(CNN)Abductions. Beatings. Torture. Summary executions of political opponents.
These are among the allegations made Wednesday against the Palestinian group Hamas in a damning new report by the international human rights watchdog Amnesty International.
During last year's Gaza conflict, which took place in July and August, Hamas used the chaos to settle scores and carry out "horrific abuses . . . some of which amount to war crimes" against fellow Palestinians, said Philip Luther, director of the Middle East and North Africa program at Amnesty International.
The report alleges that Hamas forces waged "a brutal campaign of abductions, torture and unlawful killings" against Palestinians it accused of collaborating with Israel. But some of the victims were supporters of Fatah, Hamas' political rival.
Hamas is a Palestinian Islamic organization that operates in the Palestinian territories and elsewhere in the Middle East. It controls Gaza, while Fatah, a secular party, controls the West Bank.
The U.S. State Department has included Hamas on its official list of foreign terrorist organizations since 1997.
Amnesty: Killings in public, with children watching
Among the allegations made in the Amnesty report:
• Hamas forces carried out "the extrajudicial execution of at least 23 Palestinians" and the arrest of dozens of others.
• Six men were killed by Hamas forces outside al-Omari mosque in Gaza's Old City "in front of hundreds of spectators including children."
• Palestinians abducted by Hamas "were subjected to torture, including severe beatings with truncheons, gun butts, hoses and wire or held in stress positions."
"It is absolutely appalling that, while Israeli forces were inflicting massive death and destruction upon the people of Gaza, Hamas took the opportunity to ruthlessly settle scores, carrying out a series of unlawful killings and other grave abuses," Luther said.
No action has been taken against the perpetrators, the report said.
"Not a single person has been held accountable for the crimes committed by Hamas forces against Palestinians during the 2014 conflict, indicating that these crimes were either ordered or condoned by the authorities," Amnesty said.
Hamas' military wing, Izzedine al Qassam, was responsible for many abuses, according to the report.
'His arms and legs were broken'
It cited the case of Atta Najjar, a former Palestinian police officer who had a mental disability. Najjar was serving a 15-year prison term after having been convicted of collaborating with Israel, Amnesty reported.
On August 22, Najjar was taken from prison and killed, according to Amnesty.
His brother retrieved the body.
"There were marks of torture and bullet shots on his body," the report quoted the brother as saying. "His arms and legs were broken ... His body was as if you'd put it in a bag and smashed it. ... And from behind the head -- there was no brain. Empty."
Torture and cruel treatment of detainees in an armed conflict is a war crime, Luther said.
Amnesty called on the Palestinian authorities, including the Hamas administration in Gaza, to cooperate with independent investigations, among them one conducted by the Commission of Inquiry set up by the U.N. Human Rights Council in July.