The US said its security cooperation with Saudi Arabia was not a “blank cheque” as Riyadh agreed to mount an investigation into a widely condemned air raid on funeral in Yemen that killed 140 people. In one of the deadliest attacks of the country’s civil war, which Saudi Arabia entered in March 2015, airstrikes on Saturday hit a funeral hall packed with thousands of mourners in Yemen’s rebel-held capital, Sana’a. More than 525 people were wounded. The Saudi-led coalition has not acknowledged responsibility for the attack, even as it announced an investigation, but is the only force with such air power in the conflict. The White House issued a statement saying it had begun an “immediate review” of its support for Saudi Arabia in Yemen. The attack has been condemned by the UN, the European Union and the United States. What is happening in Yemen and how Saudi Arabia's airstrikes are affecting civilians - explainer Read more The issue is embarrassing for the US since it has decried the Russian failure to be more open about its role in the air attack on a UN aid convoy in Syria, and it will face allegations of double standards if it allows the Saudis to delay an inquiry. The US, like the UK, supplies arms to Saudi Arabia and practical military advice, even though the precise extent of that advice is disputed. White House national security council spokesman Ned Simon said: “We are deeply disturbed by reports of [the] airstrike on a funeral hall in Yemen, which, if confirmed, would continue the troubling series of attacks striking Yemeni civilians. US security cooperation with Saudi Arabia is not a blank cheque. “Even as we assist Saudi Arabia regarding the defence of their territorial integrity, we have and will continue to express our serious concerns about the conflict in Yemen and how it has been waged. In light of this and other recent incidents, we have initiated an immediate review of our already significantly reduced support to the Saudi-led coalition and are prepared to adjust our support so as to better align with US principles, values and interests, including achieving an immediate and durable end to Yemen’s tragic conflict.” The UK foreign office minister Tobias Ellwood also called for the Saudis to urgently investigate. Reuters quoted Saudi officials as denying any strike and insisting its air force has clear instructions to avoid such targets. The Foreign Office has insisted UK arms export licences to Saudi Arabia do not need to be revoked since there was no serious risk of a breach of humanitarian law. Advertisement In an unexpected twist, Islamic State claimed responsibility for the attacks even though it is thought the deaths were caused by an air raid, and Isis has no access to aircraft. The Saudi-led coalition issued a statement saying it was aware of reports about the “regrettable and painful” bombing of the Great Hall in Sana’a. The coalition expressed its deepest condolences and support to the families of the victims of hostilities in Yemen since 2014. The statement added: “The coalition confirms that its troops have clear instructions not to target populated area and to avoid civilians. The coalition will immediately investigate this case along with Joint Incidents Assessment Team (JIAT) in Yemen.” A call for an independent UN-led investigation into general breaches of humanitarian law in the 18-month conflict were last month fended off by Arab states at the Human Rights Council in favour of a compromise that allows the UN to advise a national inquiry. At least 10,000 people have been killed in the 18 month conflict. Thousands of Yemenis, many armed, gathered at the UN headquarters in Sana’a on Sunday calling for an international investigation into the air raid. Radios and mosque loudspeakers throughout the city blared mourning verses as demonstrators crowded the streets around the UN headquarters, many waving their rifles in the air. The dead and wounded from Saturday’s attack include senior military and security officials from the ranks of the Houthi rebels fighting the internationally recognised government of president Abd-Rabbu Mansour Hadi, as well as their allies – loyalists of former president Ali Abdullah Saleh. Ambulances rushed to the site to ferry the wounded to hospitals. In radio broadcasts, the health ministry summoned off-duty doctors and called on residents to donate blood. Rescuers, meanwhile, sifted through the rubble in search of more casualties but a fire hindered their efforts.