GENEVA -- As the United States and Russia searched for a diplomatic solution to the crisis over Syria's chemical weapons, a four-person United Nations rights panel presented detailed evidence on Wednesday of what it said were war crimes and crimes against humanity committed by pro-government forces and, to a lesser extent, rebels in the 30-month-old conflict.
Bolstered by weapons and money from regional and global powers waging a proxy war, Syria's government and rebel forces have committed murder, torture, rape and indiscriminate attacks on civilians, without fear of future punishment, the panel, a Commission of Inquiry that was expanded last fall, said in its latest report, to be presented to the United Nations Human Rights Council here in Geneva on Monday.
The report was careful to hold both sides responsible, but the unevenness of the conflict -- with heavily armed government forces battling rebels with scanty, sometimes homemade arsenals -- was evident. Of the nine mass killings the panel investigated for the report, eight were attributed to the government side and one to rebels.
"Relentless shelling has killed thousands of civilians and displaced the populations of entire towns," the report said, leaving government responsibility implicit. "Massacres and other unlawful killings are perpetrated with impunity. An untold number of men, children and women have disappeared. Many have died in detention."
"The perpetrators of these violations and crimes, on all sides, act in defiance of international law," the report said. "They do not fear accountability. Referral to justice is imperative."
The new report echoes warnings the panel issued in February, when it reported evidence of war crimes on both sides and said the violence was worsening, with increasing sectarianism, the radicalizing influence of a growing number of foreign fighters, and "the proliferation of weapons and types of weapons used." At that time the panel urged the United Nations Security Council to refer those responsible for crimes to the International Criminal Court.
The panel's new report tracks the investigations the panel conducted over three months, ending in mid-July. It is dated Aug. 16, five days before a chemical weapons attack on a suburb of the Syrian capital, Damascus, that prompted threats of punitive military strikes by the United States and France. But its findings of continuing and even escalating atrocities underscore what is at stake as Secretary of State John Kerry and Foreign Minister Sergey V. Lavrov of Russia prepare to meet in Geneva on Thursday to try to flesh out Russia's proposal for putting Syria's chemical weapons under international control.
A successful outcome to their talks would avert American military strikes against President Bashar al-Assad's government. It might also revive efforts to convene a second Geneva conference to broker an end to the conflict.
The alternative risks the continuation or widening of a conflict that the panel says has intensified in recent months, reigniting tensions in neighboring countries and posing a wider threat to the stability of the region.
Pro-government forces had gained momentum over the summer, maintaining control of cities and major communications routes and recapturing some areas previously taken by rebel groups, the panel reported. Opposition forces, through plagued by internal strife and increasingly radicalized, had become more organized and reinforced their hold on large areas of Syria's north and east.
The panel, which has not been allowed to enter Syria, relies largely on interviews with refugees and defectors. Its new report says government forces unleashed indiscriminate bombardment by tanks, artillery and aircraft against areas they were unwilling or unable to control. The forces inflicted heavy civilian casualties "as a matter of policy," on some occasions as retribution for the presence of armed groups and on others with the perception of "a strong undercurrent of sectarianism," according to the panel.
The number of people killed in government custody "rose markedly," the panel reports, drawing on 258 interviews to give details of widespread torture, particularly by military intelligence and other security agencies. Adult detainees "regularly reported the detention and torture of children as young as 13," the panel reported. It said that "the involvement and active participation of government institutions indicated that torture was institutionalized and employed as a matter of policy."
The one massacre by opposition forces covered in detail by the panel's report was the mass killing of Shiite residents in the Hatla district of Deir al-Zour in June, according to the panel, which reported summary executions of captured government soldiers and said rebel forces had recruited children for combat. Rebel groups had also conducted torture, the report said, and although these occurred only in isolated instances, "there were strong indications that such practices are on the rise."
The panel called on the international community to halt arms transfers to Syria and to take "tangible steps to curb the increasing influence of extremists," insisting there is no possibility of a military solution.
Emphasizing the warring parties' sense of impunity, the panel pointed out that it had continued to update its list of individuals and institutions identified as responsible for crimes and atrocities. In comments to reporters earlier in the week, one panel member, Carla Del Ponte, a former chief prosecutor of two United Nations criminal law tribunals, said, "It's a long list."
This article originally appeared in The New York Times.