Griffiths also expressed shock at Houthi authorities sentencing thirty prisoners to death recently The UN envoy called on the Houthis to respect laws concerning prisoners and detainees LONDON: The UN special envoy for Yemen Martin Griffiths said on Thursday that he is “very concerned” about Houthi attacks on Saudi Arabia. Speaking at the UN, Griffiths also expressed shock at Houthi authorities sentencing thirty prisoners to death recently. Thirty men were sentenced to death by the Houthis in Yemen last week amid credible allegations that many were tortured during three years of politically-motivated detention, the UN human rights office said. The UN envoy called on the Houthis to respect laws concerning prisoners and detainees. Griffiths said he held a "productive meeting" with Saudi Arabia"s deputy defense minister Prince Khalid bin Salman on Monday in Jeddah. Tweeting about the meeting, Griffiths said he discussed with Prince Khalid how to keep Yemen out of ongoing regional tensions and how to make progress in the implementation of the Stockholm agreement with the support of the Kingdom