Individuals at the highest level from Saudi Arabia, the United Arab Emirates, the government of Yemen and Houthi rebels have committed violations of international law in Yemen that may amount to war crimes, UN experts have said.

A long-awaited report released on Tuesday catalogues abuses including rape, torture, disappearances and “deprivation of the right to life” during the three-year Yemeni conflict, in which Houthi rebels and their allies are fighting a Saudi-led coalition that backs the UN-recognised government of President Abd Rabbu Mansour Hadi.

In a particularly damning section of the report, the three experts said the Saudi-led coalition routinely failed to consult its own “no-strike list” of more than 30,000 sites in Yemen, including refugee camps and hospitals. They also said the Saudi air force had failed to cooperate with them about its targeting process.

“Despite the severity of the situation we continue to see a complete disregard for the people in Yemen,” said Charles Garraway, one of the authors of the report and a former legal officer to the British army.

The 41-page report, based on visits to many parts of Yemen, said coalition airstrikes had caused most of the documented civilian casualties, with residential areas, marketplaces, funerals, weddings, detention centres, religious sites and medical facilities hit.

“There is little evidence of any attempt by parties to the conflict to minimise civilian casualties, the group’s chair, Kamel Jendoubi, said in a statement. “I call on them to prioritise human dignity in this forgotten conflict.”

The US defence secretary, James Mattis, said the US had reviewed its support for the Saudi coalition and concluded it was right to continue. He said the US had seen “no callous disregard for human life” and the coalition’s task was “to determine what went wrong with errant bombing attacks” to “prevent it from happening again.”

Other US military officers have been sharply critical of the bombing of a school bus this month that left more than 40 dead. CNN had reported unnamed Pentagon officials so exasperated by Saudi targeting procedures that they were wiling to withdraw support.

The Saudi-led coalition said it had referred the UN report to its legal team for review. The United Arab Emirates foreign affairs minister, Anwar Gargash, said the report merited a response but he added the region needed to be preserved from “Iranian encroachment”.

The report also says that restrictions Saudi Arabia has placed on the delivery of aid by sea or air have had such a severe humanitarian impact that “such acts, together with the requisite intent, may amount to international crimes.”

The experts said they had sent a confidential list of individuals who may be responsible for international crimes to the UN high commissioner for human rights.

The report also says that the Houthi rebels and their allies loyal to the former president Ali Abdullah Saleh are also accused of impeding the delivery of aid and other important goods, particularly in the city of Taiz.

In a clear call for western countries such as the US and Britain to stop arming the two Gulf states most involved in the conflict – Saudi Arabia and the United Arab Emirates – the experts urged the international community to “refrain from providing arms that could be used in the conflict”. The remark could also be taken as a call for Iran to refrain from proving missiles to Houthi forces.

The UN human rights office says it has recorded 6,475 civilian deaths and 10,231 injuries between March 2015 and June this year.

Charles Garraway and Kamel Jendoubi of the Group of Eminent Experts on Yemen in Geneva. Photograph: Salvatore Di Nolfi/EPA

The report prompted a group of more than 50 NGOs to call for the mandate of the group of experts to be extended and strengthened when the UN human rights council meets in Geneva in September to discuss the issue.

European and Gulf states clashed over whether to establish the inquiry in the first place. The group of experts was finally set up in September 2017 with partial British backing. It is now likely that Saudi Arabia will call for the panel’s work to be ended on the grounds that it is disproportionate and biased.

The group of NGOs pointed out that Saudi Arabia had recently announced a royal pardon to all of the members of its armed forces taking part in Operation Restoring Hope, the code name for the push to reinstall Hadi as president. The charities complained “the sweeping and vaguely worded statement did not clarify what limitations if any applied to the pardon”.

The UN’s office for the coordination of humanitarian affairs in Yemen said: “What is happening in Yemen is unthinkable. It is time for everyone to wake up to the reality and human cost of this terrible war and to work together to bring hostilities to an end.”

Britain and other western powers have continued to arm Saudi Arabia, claiming there is no serious risk of it breaching international humanitarian law. A case brought in the UK high court last year to suspend the issuing of arms exports control licences failed after the court ruled the UK government had sought to minimise the risk of breaches.

The UN report, the most authoritative independent account of the war’s conduct since it began about four years ago, is likely to be citied by groups such as the Campaign Against Arms Trade in an appeal against the high court ruling.