Thousands of mourners gathered on Monday to bury dozens of children killed in a Saudi-led coalition air strike on a bus in northern Yemen.

At least 40 children were killed in Thursday’s raid which hit the bus as it drove through a market of Dahyan, a town in Saada, the armed Houthi group which controls the province said.

Cars bearing the logo of the Iranian-aligned Houthi movement transported the bodies, wrapped in white shrouds, from the hospital to a large square for prayers before heading to the graveyard, where rows of graves were dug on Friday.

People carried pictures of those killed as armed Houthi fighters managed the crowd attending the funeral.

“My son went to the market to run house errands and then the enemy air strike happened and he was hit by shrapnel and died,” said Fares al-Razhi, mourning his 14-year-old son.

“For my son, I will take revenge on Salman and Mohammed Bin Zayed,” he said, referring to leaders of Saudi Arabia and the United Arab Emirates.

The Gulf Arab states are leading the alliance of Sunni Muslim countries that intervened in Yemen’s war in 2015 to try to restore the internationally recognized government that was expelled from the capital Sanaa by the Houthis in 2014.

The coalition said on Friday it would investigate the strike after U.N. Secretary-General Antonio Guterres condemned the attack and called for an independent probe.

But on Saturday, the Saudi state news agency SPA said Saudi Arabia’s mission to the world body had delivered a message to Guterres reiterating that the military action was “legitimate” and had targeted Houthi leaders responsible for “recruiting and training young children”.

TALKS PLANNED
The coalition initially said after the attack that the strike had targeted missile launchers that were used by the Houthis to attack the southern Saudi province of Jizan.

The Houthis’ health minister Taha Mutawakil said last week that the estimated number of casualties stood at 51 killed including 40 children, and at least 79 people wounded, of which 56 were children. The International Committee of the Red Cross reported the same toll on Friday, citing authorities in Saada.

The head of the Houthis’ supreme revolutionary committee, Mohammed Ali al-Houthi, attended the funeral and blamed the United States “for this crime and all the crimes that have been committed against Yemen”, the Houthi-held al-Masirah TV said.

The United States and other Western powers provide arms and intelligence to the alliance, and human rights groups have criticized them over coalition air strikes that have killed hundreds of civilians at hospitals, schools and markets.

A U.S. military spokeswoman said U.S. forces were not involved in Thursday’s air strike. The U.S. State Department urged the Saudi-led coalition to “conduct a thorough and transparent investigation”.

The coalition says it does not intentionally target civilians and has set up a committee to probe alleged mass casualty air strikes, which has mostly cleared it of any blame.

The Houthis have also been criticized by rights groups.

The U.N. special envoy to Yemen has been shuffling between the warring parties ahead of holding consultations in Geneva on Sept. 6 in an effort to end the conflict that has killed more than 10,000 people and pushed the impoverished Arab country to the verge of starvation, according to the United Nations.