The 193-member world body adopted a resolution by a vote of 105 to 15 with 52 abstentions over strenuous objections from Syria and close ally Russia who accused the assembly of interfering in the work of the Security Council, which is responsible for issues of international peace and security.
Liechtenstein's U.N. Ambassador Christian Wenaweser, who sponsored the resolution, said vetoes in the Security Council, by Russia, "have led to inaction at the expense of the people of Syria."
"Our inaction tends to signal that war crimes and crimes against humanity are condoned and have no consequences," he said.
Wenaweser said this was why the General Assembly, where there are no vetoes, had to address the issue of accountability for violations of international humanitarian and human rights laws since March 2011, when the Syrian conflict began.
The resolution takes "one meaningful step," he said, in establishing a new body "to closely coordinate" with the Independent International Commission of Inquiry on Syria, which was established by the Geneva-based U.N. Human Rights Council. It said earlier this year that war crimes are "rampant" in Syria.
Syria's U.N. Ambassador Bashar Ja'afari called the resolution illegal, "a flagrant interference in the affairs of a U.N. member state," and "a direct threat to a solution" of the 5 1/2-year conflict which has killed more than 250,000 people.
The resolution establishes an "International, Impartial and Independent Mechanism" under U.N. auspices to closely cooperate with the Commission of Inquiry on Syria "to collect, consolidate, preserve and analyze evidence of violations of international humanitarian law and human rights violations and abuses and prepare files in order to facilitate and expedite fair and independent criminal proceedings" in the future.
It asks the secretary-general to arrange for the speedy establishment of the independent body, which will initially be funded by voluntary contributions, and urges all U.N. member states, especially parties to the conflict, to cooperate with it.
"The General Assembly today demonstrated that it can take the reins on questions of justice in the face of Security Council deadlock," said Balkees Jarrah, senior international justice counsel at Human Rights Watch.
She said countries that voted for the "unprecedented" resolution "took a critically important stand for victims of massive grave crimes."
The General Assembly will now help "pave the road to accountability after years of unchecked atrocities," Jarrah said, and "perpetrators now know that evidence of their misdeeds will be collected to hasten the day when they find themselves in the dock."
Copyright 2016 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.