All sides fighting in Syria's civil war are using shelling and siege tactics to punish civilians, and the United Nations Security Council (UNSC) "bears responsibility" for allowing such war crimes to continue, a U.N.-appointed human rights commission said Wednesday.
The independent investigators, presenting their most recent report documenting atrocities in Syria, specifically called out the UNSC for failing to refer grave violations of the rules of war to the International Criminal Court (ICC) for prosecution.
"The Security Council bears responsibility for not addressing accountability and allowing the warring parties to violate these rules with total impunity," Paulo Pinheiro, who leads the U.N. commission of inquiry, told a news conference.
"One of most stark trends we have documented is the use of siege warfare, the denial of humanitarian aid, food and basic necessities such as medical care and clean water have forced people to choose between surrender and starvation," he said.
The UNSC, whose five permanent members wield veto power over resolutions that could force the international body to intervene on behalf of Syrian civilians, is divided over the conflict, with Russia — and to a lesser extent China — blocking measures aimed at punishing Syrian President Bashar al-Assad’s government.
More than 140,000 Syrians have been killed in the conflict, which enters its fourth year next week. Intense fighting has caused an estimated 2.5 million Syrians to flee the country as refugees and has left 6.5 million people internally displaced.
The human rights commission, which includes two dozen investigators — among them former U.N. war crimes prosecutor Carla del Ponte — said all sides participating in the conflict violated rules of war enshrined in the Geneva Conventions.
The war crimes include torture, massacres, rapes and recruitment of child soldiers.
When asked specifically about Assad's responsibility, Pinheiro declined to divulge the names of individuals the commission suspected of war crimes. “We mentioned several times the responsibility of people in the high echelons in the (Syrian) government,” he said.
"The reports, if they were not able to ensure accountability in the present, I think that they will be important material for the future. But also our data bank and list of perpetrators that we have established," he added.
Despite some tactical gains by the Syrian government and its allied foreign fighters, including Lebanese Shia group Hezbollah, its fighting against armed rebel groups has reached a stalemate, causing significant casualties and material losses, the report said.
"The government relied extensively on the superior firepower of its air force and artillery, while non-state armed groups increasingly resorted to methods of asymmetric warfare, such as suicide bombs and use of improvised explosive devices," the report stated.
As part of a strategy aimed at weakening the rebels and breaking the will of their popular base, government forces have besieged and bombarded civilian areas, it explained.
"Partial sieges aimed at expelling armed groups turned into tight blockades that prevented the delivery of basic supplies, including food and medicine, as part of a 'starvation until submission' campaign."
The report also blamed anti-government rebels for the continuation of violence and suffering of civilians throughout Syria, saying that they had "inflicted severe physical or mental pain or suffering on civilian populations in areas under their control," including on prisoners.
Referring to the northern Raqqa area under the control of the ISIL, the report said: "The acts committed by non-state armed groups ... in areas under their control against the civilian population constitute torture and inhuman treatment as a war crime and, in the context of (Raqqa), as a crime against humanity."
Rebels have encircled Nubl and Zahra, besieging 45,000 people in the two Shia towns in Aleppo province, it said.
"The siege is imposed by groups affiliated to the Islamic Front, Jaish Al Mujahedeen, Jabhat Al-Nusra and the Syrian Revolutionary Front by checkpoints erected around the area and by cutting off their electrical and water supply lines."
Al Jazeera and Reuters