Public executions, amputations, lashings and mock crucifixion are a regular fixture in jihadist-controlled areas of Syria, a UN probe charged Wednesday, also accusing Damascus of repeatedly using chemical weapons against civilians.
"Executions in public spaces have become a common spectacle on Fridays" -- the Muslim holy day -- in parts of Syria under control of the Islamic State (IS), the independent Commission of Inquiry on human rights in Syria said.
In a 45-page report covering the period from January 20 to July 15, the commission also detailed a wide range of crimes against humanity and war crimes committed by the Syrian government and other armed opposition groups.
And it accused Damascus of dropping chlorine bombs on civilian areas in April -- the first time the UN has directly blamed the government for the chemical attacks.
The four-member commission detailed a litany of horrors committed by IS, including beheading boys as young as 15 and amputations and lashings in public squares as residents, including children, are forced to watch.
The group recently allowed crowds to stone two women to death in different parts of its stronghold Raqqa, said its latest report.
IS "seeks to destroy and remould humanity in its image, wreaking havoc on civilians, minorities and the basic freedoms of women and children," commission head Paulo Pinheiro told reporters in Geneva.
He described how bodies of those killed were displayed in public, "creating an atmosphere of fear and terror".
IS, which has declared an Islamic "caliphate" in an area spanning northern Iraq and eastern Syria, is also recruiting children as young as 10 and using teens in active combat and suicide-bombing missions, the report said.
The jihadists, who sparked worldwide outrage last week when they released a video showing the beheading of US journalist James Foley, are guilty of widespread crimes against humanity in Syria, the UN commission said.
Pinheiro emphasised, though, that IS "does not have the monopoly of brutality in the Syrian conflict".
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- Government chemical attacks -
Government forces, which were blamed for the lion's share of abuses and deaths in the early years after the conflict broke out in 2011, had carried out more massacres and committed murder, torture and rape against civilians, the report said.
Since January, the government's "indiscriminate firing of missiles and barrel bombs into civilian areas" had killed hundreds of men women and children every week, it said.
At the same time, the already staggering number of deaths in Syrian prisons also appeared to be on the rise and many more civilians had disappeared without a trace, said the report.
The commissioners also accused Damascus of dropping barrel bombs containing what was likely the chemical agent chlorine on civilian areas in the north on eight different occasions over a 10-day period last April.
President Bashar al-Assad's regime and rebels have both accused the other of using chemical agents in the bloody uprising.
Damascus agreed to hand over its chemical weapons to international observers after an attack last year on a rebel stronghold in the capital sparked a global outcry and the threat of US airstrikes, but it was not required to declare its chlorine stocks.
The commission said warring parties in Syria operated under an "atmosphere of impunity" and lashed out at the lack of international action to end the conflict estimated to have killed nearly 200,000 people.
"For three years, we have been gathering evidence against the perpetrators, and each day new crimes occur (yet) the international community does nothing," said commission member and former war crimes prosecutor Carla del Ponte.
"The international community as a whole, including the UN, is paralysed by the unwillingness of states to act to end the conflict," Pinheiro said, blaming global apathy for the surging extremism in Syria and the region.
They charged the UN's deadlocked Security Council to refer the Syrian crimes to the International Criminal Court, saying the commission was "ready" to prosecute a growing list of suspected perpetrators.