Washington (AFP) - At least 10 air strikes carried out by a Saudi-led coalition in Yemen broke the laws of war and killed civilians, Human Rights Watch alleged Friday.

The strikes are listed in a major new report by the watchdog, which estimates that 2,500 Yemeni civilians have died in coalition strikes since March.

Saudi Arabia, the UAE and other Arab allies -- with logistical support from the United States -- are battling Huthi rebels on behalf of the Yemen government.

Riyadh has furiously denied previous reports of indiscriminate bombing, but Friday's detailed report cites a wealth of witness testimony.

The strikes in the report killed at least 309 civilians, wounded at least 414 and were in breach of the allies' obligation to investigate alleged war crimes.

"Human Rights Watch found either no evident military target or that the attack failed to distinguish civilians from military objectives," the report said.

"Human Rights Watch is unaware of any investigations by Saudi Arabia or other coalition members in these or other reported cases."

The 10 suspect attacks took place in Huthi-controlled Sanaa, Amran, Hajja, Hodeida and Ibb and hit residential houses, market places, a factory and a civilian prison.

Washington has given strong diplomatic backing to the Saudi offensive and earlier this month approved a $1.29 billion sale of bombs to renew its ally's arsenal.

A US State Department spokeswoman said it was aware of the Human Rights Watch report and that "any loss of civilian life in a conflict is tragic."

She blamed the Huthi side for starting the war in the first place and noted that the report also accuses the rebels of shelling civilian areas.

But the spokeswoman added: "We have asked the Saudi government to investigate all credible reports of civilian casualties resulting from coalition-led airstrikes and, if confirmed, to address the factors that led to them."

Britain and France are also major arms suppliers to Saudi Arabia and its Emirati ally.

Human Rights Watch urged the United Nations Security Council to investigate its allegations and to remind the warring parties of their legal responsibilities.