Lynn Maalouf, Amnesty International's Middle East research director, said: "The UK, USA and other states should do everything in their power to prevent further violations... they should start by immediately stopping the flow of arms to the country and end the Coalition's arbitrary restrictions on humanitarian assistance and essential imports".
The conflict has resulted in at least 16,700 casualties, including 6,475 civilians killed, but the real figure is nearly certainly significantly higher, according to the United Nations.
United Nations human rights experts say that the Saudi-led, Western-backed coalition fighting in Yemen may have committed war crimes by conducting indiscriminate airstrikes on civilians.
The Yemen government and coalition of forces, including Saudi Arabia and the United Arab Emirates, are conducting the airstrikes, the group said.
Media captionThe conflict in Yemen has been raging for years - but what is it all about? The UN says the three-year air war has killed at least 6,475 people, and probably many more.
Mohammed Albukhaiti, a Houthi political official, criticized the report, saying it equated the "intentional crimes" against civilians by the coalition with "mistakes" made by the rebels.
Experts say Saudi Arabia's perception of USA military failings in the Middle East has sunk Washington's credibility as it has sought to avert civilian casualties in Yemen. The group also documented rapes of male detainees by UAE personnel, and of women in a migrant detention facility in Aden by government-controlled security forces.
The main cause of civilian casualties in the war, the report says, has been airstrikes by the Saudi-led coalition.
Defense Secretary Jim Mattis on Tuesday defended the US backing of the Saudi-led coalition, but said it was conditioned on the Saudis doing "everything humanly possible" to avoid civilian casualties.
United Nations experts have called on Britain and the USA to stop giving weapons to Saudi Arabia for its campaign in Yemen amid evidence that Western bombs are being used in potential war crimes.
"We determined that it was the right thing to do", Mattis said.
Fighters of the Houthi movement have fired missiles into Saudi Arabia, blocked delivery of supplies to Taiz and shelled the strategic city from the highlands, the panel said. The U.S. supplies numerous precision weapons used in Saudi coalition airstrikes, and provides other limited support, including aerial refueling for coalition jets.
The report said "If there are errors in the targeting process that effectively remove the protections provided by worldwide humanitarian law, these would amount to violations".
Yemeni children gather outside their classroom in December 2016, at a school that was recently damaged in a Saudi-led air strike in the country's third-city of Taez.
The US goal was to "keep the human cost of innocents being killed accidentally to the absolute minimum" and to bring the warring parties to the negotiating table, Mattis told reporters.