The Palestine Liberation Organisation said Israeli Prime Minister Benjamin Netanyahu blatantly manipulated the facts when he compared Hamas with the Islamic State group in a UN speech on Monday.
"Netanyahu's speech at the UN was a blatant manipulation of facts and attempted at misleading the audience through a combination of hate language, slander and argument of obfuscation," PLO executive member Hanan Ashrawi said in a statement in English.
"Obviously Netanyahu has lost touch with reality, particularly in refusing to acknowledge the fact of the occupation itself or the actions of the Israeli army of occupation in committing massacres and war crimes," she added.
Addressing the United Nations General Assembly earlier, Netanyahu denied accusations of Israeli war crimes during its July-August offensive on the Gaza Strip that killed 2,140 Palestinians, mostly civilians, and left the enclave in ruins.
He instead said that Palestinian president Mahmud Abbas was jointly culpable with Hamas, which fired thousands of rockets into Israel, bringing retaliatory Israeli air strikes down on Gaza residents.
"Hamas embedded its missile batteries in residential areas and told Palestinians to ignore Israel's warnings to leave," Netanyahu said.
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"I say to president Abbas, these are the war crimes committed by your Hamas partners in the national unity government which you head and you are responsible for,' he said.
The Islamic State jihadists, and Hamas, Netanyahu added, "share a fanatical creed, which they both seek to impose well beyond the territory under their control."
In Gaza, Hamas spokesman Sami Abu Zuhri said Netanyahu was "portraying Hamas and IS as two faces of the same coin" although "Hamas is a national liberation movement, while the (Israeli) occupier is the source of evil and terrorism in the world".
In his own address to the General Assembly on Friday, Abbas vowed to seek war crimes prosecutions against Israel over the 50-day conflict in Gaza, which he called a "war of genocide".
Netanyahu hit back on Monday with a jibe at Abbas's 1980 doctoral thesis in which he questioned whether six million Jews were really killed in the Holocaust.
"In what moral universe does genocide include warning the enemy's civilian population to get out of harm's way?" he asked.
"I suppose it's the same moral universe where a man who wrote a dissertation of lies about the Holocaust, and who insists on a Palestine free of Jews... can stand at this podium and shamelessly accuse Israel of genocide and ethnic cleansing," he said.
In his address last week to the 193-nation Assembly, Abbas asserted that years of peace negotiations had failed, stressing that Israel was forging ahead with settlements and maintaining a blockade of Gaza despite formal pledges of peace.
The latest round of Israeli-Palestinian talks, fostered by US Secretary of State John Kerry, collapsed in April amid bitter recriminations on both sides.