A panel set up by the Saudi-led coalition fighting in Yemen to investigate civilian casualties found a series of deadly air strikes largely justified, citing the presence of armed militiamen at the homes, schools and clinics that were targeted.

The Joint Incidents Assessment Team said on Tuesday it had discovered mistakes in only three of 15 incidents it reviewed, and maintained the coalition had acted in accordance with international humanitarian law. Saudi Crown Prince Mohammed bin Salman has long been running the coalition fighting in Yemen as the country's defense minister, a title he still retains.

Saudi Arabia and its allies have been bombing the Iran-aligned Houthi movement since the Houthis seized much of northern Yemen in 2015.

The Houthis have in turn fired rockets towards Saudi cities and villages. They say their attacks are in response to Saudi strikes on Yemeni cities and villages. The war has killed more than 10,000 people.

The coalition has been repeatedly criticised for civilian casualties. Human Rights Watch accused it on Tuesday of war crimes, saying air strikes that hit family homes and a grocery store were carried out either deliberately or recklessly, causing indiscriminate loss of civilian lives.

The United Nations said on Monday it had verified 5,144 civilian deaths in the war, mainly from coalition bombardment, and an international investigation was urgently needed.

"The minimal efforts made towards accountability over the past year are insufficient to respond to the gravity of the continuing and daily violations involved in this conflict," U.N. human rights chief Zeid Ra'ad al Hussein said in Geneva.

Speaking in the Saudi capital Riyadh on Tuesday, the panel's legal advisor, Mansour Ahmed al-Mansour, told journalists the coalition had made "an unintended mistake" in bombing a water well-drilling rig north of Yemen's capital Sanaa last year after confusing it with a ballistic missile launcher.

The raid reportedly killed 30 people and JIAT recommended the coalition provide "appropriate humanitarian assistance", without elaborating.

It urged the same for strikes in Sanaa in June and September 2015 when bombs targeting military objectives mistakenly hit civilian buildings due to "a technical malfunction in aircraft systems".

Mansour denied the coalition hit a U.N. compound in Aden in June 2015, which the U.N. secretary general said at the time caused serious structural damage and one casualty.

About a January 2016 attack near Saada which killed a Medecins Sans Frontieres ambulance driver and at least five other people, Mansour disputed the vehicle was clearly marked and said the coalition had legitimately targeted it and an ammunition depot it was parked beside.

"The vehicle was used for military purposes due to the secondary explosion in the vehicle, which was obvious," he said.

The investigators also absolved the coalition of responsibility for attacks on a Coca-Cola factory in December 2015 and a centre for the blind the following month.