( CNN ) -- The Syrian war has never been a simple fight between good rebels and evil government forces , and the United Nations has said so several times in the past . But this week , U.N. investigators released a particularly detailed and horrific report that slams both sides , accusing rebels fighting to oust President Bashar al-Assad of murder , rape , torture and forced disappearances . Government forces and the rebels have violated international humanitarian law in the two-year war , said Paulo Pinheiro , chairman of the U.N . Independent International Commission of Inquiry on Syria . `` The war displays all the signs of a destructive stalemate , '' he told the U.N. Security Council this week . `` If the national , regional and international actors fail to find a solution to the conflict and stop the agony of millions of civilians , '' Pinheiro warned , `` the alternative will be the political , economic and social destruction of Syria and its society , with devastating implications for the region and the world . '' The lengthy report is based on information from 443 interviews that U.N. investigators conducted inside Syria . One of the more disturbing passages details rebels and government forces recruiting boys as young as 12 . Children under 18 are seized at checkpoints , and government-affiliated militia use sectarian affiliation , kinship systems and cash to cajole children into their ranks , the paper notes . The government has used children as informants , but both they and rebels punish children who act as informants by killing them , the report says . An uncorroborated video , investigators say , seems to show a child associated with an anti-government group beheading a prisoner . The report says rebels frequently use schools as barracks or offices , children have taken up arms to fight and rebels have used them as lookouts . In other violations , both groups have also targeted typically off-limits groups like medical workers and indiscriminately shelled each other , killing innocents caught in the crossfire . Two million Syrians have been internally displaced , and more than 4 million need humanitarian aid , the investigators found . The United Nations has repeatedly called for more serious and sustained international attention to Syria and a diplomatic end to the fighting . But the war has affected the body itself . Last week , rebels detained 21 U.N. peacekeepers , claiming they came into an area where they did n't belong and saying they suspected the peacekeepers were secretly trying to help government forces . The captives were released a few days ago . Rebels on Tuesday said the report was an exaggeration . Louay Almokdad , a spokesman for the rebel Free Syrian Army , said he was shocked by the report . `` We are quite stunned that the U.N. would issue such a report and try to blame both sides for violations when it is clear who is committing atrocities in the country and who is killing our innocent civilians , '' Almokdad said . The Syrian government , meanwhile , has consistently blamed `` armed terrorist groups '' for killing civilians . While the regime has often referred to opposition fighters as `` terrorists , '' some radical militants -- such as members of the Nusra Front -- have also joined the fight against the government . Last year , the United States blacklisted the Nusra Front as a foreign terror organization . The move baffles Syrian rebels , an analyst said . Many Syrians see the group as heroes of the revolution because of its professionalism and its willingness to fight and take causalities , said Jeffrey White , a defense analyst at The Washington Institute for Near East Policy . The organization is active in eight provinces , he said . More than 70,000 Syrians -- mostly civilians -- have been killed since peaceful anti-government protests led to a fierce government crackdown , an armed uprising and a civil war with no end in sight . On Tuesday , U.S. Secretary of State John Kerry urged patience . `` You have to have some patience in this process even as you approach it with care , and I think that 's exactly what we are doing , '' he told reporters in Washington . `` We want to stop the killing . And they want to stop the killing . The world wants to stop the killing , '' he said .
NEW : U.S. Secretary of State John Kerry urges patience : `` We want to stop the killing '' Rebels say they are shocked the U.N. would accuse them of atrocities . Both government and rebel forces are accused of recruiting boys . U.N. panelist : No diplomatic end to war means `` devastating '' implications for the region and world .