ADEN, Sept 20 (Reuters) - The European Union joined a chorus of international criticism on Monday over the execution of nine men by the Iran-aligned Houthi movement in Yemen following their conviction for involvement in the killing of the group"s top civilian leader. Saleh al-Samad, who held the post of president in the Houthi-controlled administration which runs most of northern Yemen, was killed in April 2018 by a Saudi-led coalition air strike in the port city of Hodeidah on Yemen"s west coast. A Houthi court found the nine men, including one who was a minor when he was arrested, guilty of spying and sharing sensitive information with the Saudi-led coalition. They were executed on Saturday by firing squad. read more Pictures and videos of the executions have been widely shared on social media, which showed military officers shooting the nine men in the back in Sanaa"s central public square. In a statement condemning the executions, an EU spokesperson said there had also been reports of irregularities in the judicial process and allegations of mistreatment. "The European Union strongly opposes the death penalty at all times and in all circumstances. It is a cruel and inhumane punishment...," said the statement. Earlier, U.N. Secretary-General Antonio Guterres issued a similar statement in which he also called for a moratorium on use of the death penalty in Yemen and for a peaceful negotiated settlement of the conflict there. The U.S. embassy in Yemen condemned what it called "a sham trial following years of torture and abuse" by the Houthis. Britain said the executions demonstrated "indifference to human dignity & blatant disregard for fair trial & due process". The Houthis" foreign ministry dismissed the criticism as "interference in domestic affairs" and accused the United Nations and the West of turning a blind eye to the "coalition"s crimes". Samad was the most senior official to be killed by the coalition in the years-long war in which the Houthis are fighting forces loyal to the internationally-recognised government based in the southern port city of Aden.