Serious violations of international laws amounting to war crimes were committed during the battle for Aleppo last year, a report to the UN has said.
Civilians caught up in the fighting between July and December 2016 were "increasingly left vulnerable to repeated violations by all sides", the report by the Independent International Commission of Inquiry on the Syrian Arab Republic said.
The use of chlorine bombs by Syrian forces, resulting in "civilian casualties, many of them children", was also detailed in the report.
The report, which described the battle war as "a stage of unrelenting violence", said: "The use of chlorine, regardless of the presence of a valid military objective, is prohibited by customary international humanitarian law."
It added: "The continued use of chlorine by Syrian forces evinces a blatant disregard for international legal obligations, and also amounts to the war crime of indiscriminate attacks against a civilian population."
'Surrender or starve'
The report also condemned "brutal" tactics used by pro-government forces, which it accused of deliberately starving civilians.
It said the siege "simultaneously deprived civilians of freedom of movement and prevented basic commodities, including food and medical supplies, from entering the city".
The "widely used" tactic of "surrender or starve" had "proven disastrous of civilians", the report added.
It concluded: "While the deprivation of supplies might have ultimately forced armed groups to surrender, the achievement of this result was accelerated by daily Syrian and Russian airstrikes, which claimed hundreds of lives and destroyed vital civilian infrastructure."
Attacks on hospitals and aid convoys
The 37-page report also accused Syrian forces of deliberately obstructing the delivery of humanitarian aid, while bombarding hospitals which did not have military targets "in or around the vicinity".
It described an airstrike on a humanitarian aid convoy which killed 15 aid workers as "one of the most egregious".
"Syrian forces committed the war crimes of deliberately attacking humanitarian relief personnel, denial of humanitarian aid, and attacking civilians," said the report.
It added that the same hospitals were "repeatedly bombarded" within two specific time frames, which "strongly suggests that pro government forces committed the war crimes of intentionally targeting protected objects, medical personnel and transport."
The report, based on 291 interviews, including with residents of Aleppo city, also detailed how "Syrian and/or Russian air forces pervasively used cluster munitions", which killed and injured civilians.
It said the "inherently indiscriminate weapon" was used in densely populated areas such as eastern Aleppo "constituting the war crime of indiscriminate attacks in a civilian populated area".
In a damning verdict on all parties, the report concluded: "Throughout the siege of eastern Aleppo, armed groups continuously shelled western Aleppo using mostly unguided and imprecise weaponry, such as improvised rockets and mortars.
"The nature of the weapons used and the absence of a military presence in the majority of cases reviewed terrorized residents of western Aleppo in violation of the international humanitarian law principle of distinction. These attacks therefore amount to the war crime of indiscriminate attacks against a civilian population."
'Civilians shot to stop them leaving'
As it became clear that the battle for Aleppo nearing its end, the report states how "all parties continued to commit brutal and widespread violations" with civilians shot by armed groups to stop them from leaving.
Some civilians were "effectively used as human shields" while others were arrested and their whereabouts remain unknown.
In the evacuation of eastern Aleppo, thousands of civilians were forced to move to government-controlled western Aleppo while others were taken to Idlib where they are once more living under bombardments.
The report said: "In line with the precedents of Moadamyia and Darayya, this agreement confirms the regrettable trend whereby parties to the conflict in Syria use civilian populations as bargaining chips for political purposes."
Commissioner Karen AbuZayd said: “Some of these agreements amount to forced displacement. It is imperative that the parties refrain from similar future agreements and provide the conditions for the safe return of those who wish to go back to their homes in eastern Aleppo."