The top United Nations aid official has called for a swift investigation of a suspected Saudi - led coalition air strike that killed dozens of people at a wedding party in Yemen. Stephen O'Brien, the UN under-secretary-general for humanitarian affairs, said on Friday that he was "deeply disturbed" by the news that civilians had been killed in Wednesday evening's bombing. "I call for a swift, transparent and impartial investigation into this incident," O'Brien said in a statement. "Real accountability for parties to conflict, whether they are states or non-state groups, is urgently needed, to ensure that the commitment under international law to protect civilians is meaningful," he added. O'Brien quoted Yemen's Ministry of Public Health as saying that at least 47 people were killed and 35 were injured, among them many women and children, in the strike.