The militant group Hamas tortured and killed Palestinians during the war against Israel in the Gaza Strip last year, Amnesty International said in a report released Wednesday.
Hamas, which controls Gaza, arrested and tortured dozens of Palestinians and executed at least 23, the human rights group reported.
Hamas exploited the fighting against Israel in July and August to "ruthlessly settle scores," including with members of Fatah, the rival political faction and political base of the West Bank-based Palestinian Authority, which is led by Mahmoud Abbas, according to Amnesty.
"It is absolutely appalling that while Israeli forces were inflicting massive death and destruction upon the people in Gaza, Hamas forces took the opportunity to ruthlessly settle scores," Phillip Luther, the organization's Middle East and North Africa program director, said in a news release.
Using the "chaos of the conflict," Hamas carried out "spine-chilling actions, some of which amount to war crimes," Luther said.
Hamas official Salah Bardawil said the report was not objective or balanced. It aims to divert attention from Israeli crimes against the people of Gaza, he said.
"Amnesty should have investigated the war crimes against humanity committed by Israel instead of criticizing the victims," Bardawil said.
According to the Amnesty report, among the victims was Atta Najjar, formerly a police officer of the Palestinian Authority, who was serving a 15-year prison sentence after being arrested in 2009, two years after Hamas' violent takeover of the Gaza strip, and convicted of collaborating with Israel. Najjar was taken from the prison and executed in August, a few days before a cease-fire took effect, Amnesty reported.
On the same date, six men were executed before a crowd of hundreds that included children. The report says Hamas had declared them collaborators who had been sentenced to death in "revolutionary courts" before they were dragged on the ground to be shot individually, and then sprayed with bullets.
"The Hamas leadership repeatedly calls for rights and justice for Palestinians in Gaza and elsewhere but they do not always act in a manner that reflects respects for rights, justice and the rule of law," Luther said.
Luther accused Hamas forces of flouting fundamental rules of international humanitarian law.
"Torture and cruel treatment of detainees in an armed conflict is a war crime. Extrajudicial executions are also war crimes," he said, and urged Palestinian authorities -- including Hamas -- to cooperate with international inquiries on the summer conflict, and investigate the cases documented in the report.
More than 2,100 Palestinians were killed during the fighting and it remains unclear how many were militants. The United Nations and human rights groups say most were civilians. Israel says hundreds were Hamas fighters. Almost all of the 72 killed on the Israeli side were soldiers.
In previous reports, Amnesty has accused Israel and Hamas of violating international law.
In March, the organization declared that Hamas and other militant groups had shown "flagrant disregard for international humanitarian law" with indiscriminate rocket fire into Israel. Last year, the organization said Israeli forces had "brazenly flouted the laws of war" and shown "callous difference to the carnage" inflicted by the army's attacks on civilian targets.