United Nations director of humanitarian operations John Ging has warned Yemen is on the "verge of famine" due to a "shocking fall-off" in funding.
Mr Ging, an Irish national who has completed a visit to Yemen, revealed only 16 per cent of the $1.8 billion (€1.6 billion) needed to support 7.6 million needy Yemenis has been forthcoming.
He said the UN had been able to reach only one-third of the 180,000 children suffering from acute malnutrition.
Donors for 2016 include the US, Britain, the European Commission and Japan, but not Saudi Arabia and its Gulf allies involved in air operations against Houthi forces which seized the capital Sana'a in September 2014.
Last year, the Houthis forced Saudi-backed President Abed Rabbo Mansour Hadi into exile in Riyadh.
Mr Ging visited the city of Amran where he viewed the devastation caused by air strikes that caused 1,500 job losses at a levelled cement factory. He said 300,000 people in the deprived Amran governorate had been made homeless by the war.
The crisis caused by war has been deepened by a Saudi blockade preventing the delivery of food, medical supplies and fuel to Yemen, the poorest country in the region before the conflict.
The UN has taken eight months to mount a monitoring operation to ensure deliveries of civilian supplies while enforcing an arms embargo targeting the Houthis as well as al-Qaeda in the Arabian Peninsula and Islamic State, which have exploited the conflict to seize territory.
Amnesty International has accused Shia rebel Houthi tribesmen supported by troops loyal to former president Ali Abdullah Saleh – who was ousted in 2012 – of carrying out "a wave of arrests of . . . opponents, arbitrarily seizing critics at gunpoint and subjecting some to enforced disappearance as part of a chilling campaign to quash dissent in areas of Yemen under [their] control".
In a 44-page report, Where is my Father? Detention And Disappearance in Houthi-Controlled Yemen, covering December 2014-April 2016, Amnesty says the Houthis have arrested "political opposition figures, activists, human rights defenders and journalists," tortured some and held many for up to 17 months without trial.
Amnesty says since the March 2015 intervention by Saudi Arabia and its Gulf partners, “fighting has been brutal. . . with all sides displaying flagrant disregard for civilian life . . . More than 3,000 civilians have been killed, more than half in air strikes by the Saudi Arabia-led coalition, and over 2.8 million people have been displaced.”
On Tuesday, the government suspended participation in peace talks, rejecting the Houthi demand for the formation of a powersharing unity government.
Speaking in Riyadh, prime minister Ahmed bin Dagher called upon the Houthis and their allies to withdraw from cities they control and recognise the “legitimacy” of the Hadi government.
He also said $4 billion (€3.6 billion) is missing from the central bank in Houthi-held Sana’a and could force the country to declare bankruptcy. Before the breakdown in the talks, an agreement was said to have been close.