ADEN: Saudi air strikes killed 20 civilians in a rebel-held port city of western Yemen, a government official said Thursday in a rare admission of a possible “error” by the alliance.

The coalition's spokesman, however, said the raid on Wednesday night targeted rebel leaders.

The strikes came as Riyadh faces mounting international scrutiny over civilian casualties in its 18-month campaign against Houthi rebels and their allies in Yemen.

The Suq al-Hunod district of the Red Sea port of Hodeida was hit, the official in President Abedrabbo Mansour Hadi's government told AFP.

He said the residential neighbourhood was “probably hit in error”.

General Ahmed Assiri, the coalition spokesman, told AFP the raid targeted “Houthi leaders” but the coalition did not have a count on the number killed because it is “not on the ground” there.

“We had information that they were having a meeting, then we hit them.” Assiri said any allegations of wrongdoing would have to be verified.

“We will investigate to know what has happened exactly,” he said.

US officials -- whose country supplies bombs dropped by the coalition -- have regularly urged their Saudi allies to avoid harming non-combatants.

The rebel administration in the capital Sanaa also reported the Hodeida strikes, saying there were civilian casualties.

The Houthi rebels had been celebrating the second anniversary of their seizure of Yemen's capital city.

Khaled Suhail, a doctor at Hodeida's Al-Thawra Hospital, said his facility received 12 dead and 30 wounded from the strikes.

Pictures from Suq al-Hunod showed residents combing the rubble under arc lights in a search for survivors.

The body of one child lay in a morgue, his head bloody above a left eye which remained open in death.

Air strikes by the Saudi-led coalition are suspected of causing around half of all civilian deaths in Yemen, a United Nations report said last month.

It called for an independent international body to investigate an array of serious violations by all sides in Yemen, where nearly 4,000 civilians have died.

'Growing pressure'

“In this case a misguided munition hit a neighbourhood by error, which is densely populated,” said Andreas Krieg of the Defence Studies Department at King's College London.

“It is tragic but unfortunately the reality of air power warfare in complex environments where the enemy intentionally mingles with the civilian population,” he told AFP.

Peter Salisbury, an associate fellow at London's Chatham House think-tank, said British and US arms suppliers were coming “under growing pressure” to explain their failure to influence the Saudis over civilian casualties.

“It's difficult to see what strategic advantage the Saudis are gaining from their bombing campaign outside of the front lines,” he told AFP before the Hodeida incident.

Last month, the US military said it had slashed the number of intelligence advisers directly supporting the Saudi-led coalition's air war in support of Hadi's government.

The reassignment of personnel, around June, came because “there was not the same sort of requests coming in for assistance”, Fifth Fleet spokesman Lieutenant Ian McConnaughey said.

US cooperation with Saudi Arabia mostly involves “imagery that allows them to better assess the situation on the ground, and then advice and assistance”, he said.

Targeting is ultimately decided by the Saudis, McConnaughey added.

Riyadh formed the Arab coalition which began air raids in March last year, and later sent in ground forces, to support Hadi's internationally recognised government after the Houthi and their allies overran much of Yemen.

The coalition has told AFP it uses highly accurate laser- and GPS-guided weapons and verifies targets many times to avoid civilian casualties.