"This war has been and remains an ugly war," Anwar Gargash, the United Arab Emirates (UAE) minister of state for foreign affairs, told a news conference in Dubai.

A coalition strike last Thursday hit a bus in Huthi rebel-held northern Yemen, killing at least 29 children, according to the International Committee for the Red Cross.

Huthi officials gave a death toll of 51, including 40 children, and labelled the raid a "crime by America and its allies against the children of Yemen".

The coalition announced afterwards that it had ordered an investigation into the strike, which it initially said had targeted Huthi rebel combatants.

"In this war we have seen civilians shot at, bombed, killed and, unfortunately, this is really part of any confrontation," Gargash said, adding that both sides in the conflict had been to blame.

"War is not something that can be actually a clean operation," said the UAE minister.

Gargash played up the coalition's probe into the incident.

"In various conflicts many parties have not allowed neutral or independent investigations," he said.

The minister said those calling for independent investigations should instead urge the coalition "to tighten the rules of engagement".

Mourners held a mass funeral Monday for the victims of the bus attack in the northern Yemeni city of Saada, where demonstrators vented their anger at Saudi Arabia.

The coalition intervened in Yemen in 2015 in a bid to restore the internationally recognised government of President Abedrabbo Mansour Hadi after the Iran-backed Huthis drove his government out of the capital Sanaa.

The war has left around 10,000 people dead, the vast majority of them civilians, and triggered what the United Nations has called the world's worst humanitarian crisis.