A Palestinian boy holds a Hamas flag over a destroyed house in Beit Lahia in the northern Gaza Strip on Jan. 19, a day after fighting ceased in Israel's 22-day military offensive against the Palestinian militant group. (Hatem Moussa/Associated Press)Amnesty International issued a scathing report Thursday accusing Israel and Hamas of committing war crimes during a 22-day conflict in the Gaza Strip last December and January.

The human rights organization said Israel killed hundreds of unarmed Palestinian civilians and destroyed thousands of homes in Gaza in attacks that "breached the laws of war."

An Israeli woman walks under the damaged roof of a closed food market minutes after a rocket fired by Palestinians militants from Gaza hit Sderot, southern Israel, on Jan. 5. (Bernat Armangue/Associated Press)The report also criticized the Israeli military's use of highly incendiary white phosphorus and other imprecise weapons in densely populated areas, and accused Israeli forces of preventing medical care from getting to those inside the coastal territory who needed it.

The rights group also condemned the Palestinian militant group that controls Gaza for endangering Israeli civilians by indiscriminately firing rockets at towns and villages in southern Israel.

But the bulk of the 117-page report's criticism is directed at Israel, with the report's author, Donatella Rovera, calling the scale and intensity of the destruction inflicted on Gaza unjustifiable in military terms.

"Those who have been responsible should be held accountable and the victims should get some sort of reparation," Rovera said Thursday.

Israel has dismissed accusations that it committed war crimes during the Gaza offensive, launched to curb almost daily and indiscriminate Palestinian militant rocket attacks on Israeli civilians in the south following the collapse of a six-month ceasefire with Hamas.

The Israeli military said it never deliberately targeted civilians and blamed Hamas for any civilian casualties. It said it held its own investigations and found its army acted appropriately during the offensive.

But the report said Amnesty investigators found no evidence of Hamas using Palestinian civilians as human shields, as Israel has repeatedly claimed, although it did accuse the militant group of firing rockets from densely populated residential areas.

Report biased, not transparent: Israeli spokesman

Responding to the report Thursday, an Israel government spokesman accused Amnesty of anti-Israel bias, shoddy research and a lack of transparency in its investigation.

"We made every possible effort to be as surgical as possible in a very intense urban combat situation," spokesman Mark Regev said. "We did not want to see the innocent, uninvolved population of Gaza suffer in this."

Hamas spokesman Fawzi Barhoum denounced the report, saying it "equated the victim and the executioner, and denied our people's right to resist the occupation."

"The report ignores the scale of destruction and serious crimes committed by the occupation in Gaza … and provides a misleading description in order to reduce the magnitude of the Israeli crimes," Barhoum said Thursday.

The Amnesty report said that of some 1,400 Palestinians killed during the 22-day offensive, 900 were civilians. Among them were 300 children, it said.

Israel insists the number of "uninvolved" Palestinians killed during the offensive is less than 300, and puts the total Palestinian death toll at around 1,100.

It has also repeatedly refused to co-operate with Amnesty and other international groups seeking to investigate the Israeli military's conduct during the conflict, which ended on Jan 18.

The United Nations has appointed veteran South African war crimes investigator Richard Goldstone to examine the conduct of both sides during the conflict.

Hamas allowed Goldstone and his team into Gaza last month, but Hamas security often accompanied them, raising questions about the ability of witnesses to freely describe the militant group's actions.

Israel has refused to co-operate with the UN probe, claiming the council overseeing the investigation is biased.

With files from The Associated Press