The Syrian government is carrying out a sustained air campaign against the civilian population of the country's largest city, Aleppo, using crude and imprecise explosive devices called "barrel bombs" in what amounts to war crimes, according to an Amnesty International report released Tuesday.

"Civilians in opposition-controlled areas of Aleppo have been bombarded in their homes, hospitals, schools, public markets and places of worship in air attacks launched by government forces," the report stated.

"The majority of attacks in this campaign have involved the use of "barrel bombs" – large, improvised explosive devices, which are delivered from helicopters and consist of oil barrels, fuel tanks or gas cylinders that have been packed with explosives, fuel and metal fragments to increase their lethal effect," it added.

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You can read the report in its entirety here.

With the conflict in its fifth year and more than 200,000 people killed and 11 million Syrians displaced from their homes, the report is a staggering reminder of the scale and ways that the Syrian government and opposition groups are targeting each other – and with civilians paying the heaviest price. The picture is all the more bleak because there is no political solution or end to the civil war in sight.

"Immediately you're hit with the carnage and the level of atrocities are just so high. This is not anything new to those of us who follow Syria. We've seen tons of these reports come out – the report by Amnesty is just the latest one," said Andrew Tabler, senior fellow at the Washington Institute for Near East Policy.

Mr. Tabler points to a trove of 55,000 photographs showing torture, starvation and death, allegedly at the hands of the Syrian government. The photos were released by a Syrian defector who goes by the pseudonym Cesar and who fled the country in 2013. In his testimony to a U.S. congressional committee last year, he outlined how the regime of Bashar al-Assad was holding 150,000 Syrians in prisons.

The Amnesty International report does not spare criticism of opposition groups – also accusing them of war crimes. There are 18 different armed opposition groups in the Aleppo area, including al-Nusra Front, the Syria-based al-Qaeda affiliate.

The armed groups control parts of the city and often target neighbourhoods held by government forces using mortar firing, which can be imprecise and indiscriminate and result in civilian deaths and injuries. The report also states that some attacks carried out by armed opposition groups may also be a deliberate targeting of civilians, which would also mean that they are war crimes.

The United Nations started hosting separate talks on Tuesday in Geneva with rival sides in the Syrian conflict. The search for a political solution is stalled and there is little expectation that Staffan de Mistura, a Swedish-Italian career diplomat, will be able to deliver a breakthrough. His two predecessors both tried and failed.

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"Normally what is required for a negotiated settlement of a civil war is for the parties to reach a point of exhaustion and stalemate. And even though one could argue that there's been a stalemate more or less in Syria for a while now, the parties themselves don't seem to be ready to negotiate in earnest – and I think it's partly because they're continuing to receive all this outside support," said Roland Paris, an associate professor at the University of Ottawa and founding director of the Centre for International Policy Studies.

Professor Paris points to the Assad regime receiving financial and military support from Iran, Hezbollah and Russia, while opposition groups are being armed by Saudi Arabia, Qatar and Turkey, he added. The U.S., meanwhile, is aiming to train up to 5,500 rebels a year and continues to show caution around getting too involved in the Syrian civil war, Prof. Paris said.

In February 2014, the United Nations Security Council adopted a resolution that called on all sides in the conflict to stop the indiscriminate use of weapons in populated areas.

The Amnesty International report outlines regular violations of the resolutions by all sides.

In particular, it takes a closer look at the use of "barrel bombs" by the Syrian government and eight attacks that killed 188 civilians and just one opposition fighter.

"These and other factors examined in this report suggest that the aerial bombardment campaign conducted by government forces in Aleppo city deliberately targeted civilians and civilian objects," the report stated.

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"It is a war crime to intentionally make civilian objects and civilians who are not directly participating in hostilities the target of attacks. Such a systematic attack on the civilian population, when carried out as part of government policy as appears to have been the case in Aleppo, would also constitute a crime against humanity," the report added.