RNA - Ismail Ould Cheikh Ahmed made the request in a statement issued on Thursday, saying that he was "very worried about violations of the truce."
The UN official urged all sides in Yemen to "strictly respect a cessation of military operations... to allow the flow of aid."
Saudi Arabia’s pounding of Yemen continues unabated despite the declaration of the five-day ceasefire in the war-wracked country on Tuesday.
Local sources said at least nine Yemenis were killed in an Apache helicopter attack in the al-Safiya region in northwestern Sa’ada Province on Thursday.
On Wednesday, Yemen's Arabic-language al-Masirah satellite television network reported that Saudi warplanes hit the district of Malahidh in Sa’ada.
Saudi Arabia started its military aggression against Yemen on March 26 - without a UN mandate - in a bid to undermine the Houthi Ansarullah movement, which currently controls the capital, Sana’a, and other major provinces, and to restore power to the country's fugitive former president, Abd Rabbuh Mansur Hadi, who is a staunch ally of Riyadh.
Meanwhile, the UN Food and Agriculture Organization recently warned of a “catastrophic” humanitarian situation in Yemen, saying more than 15 million Yemenis are suffering from food insecurity in the wake of the Saudi airstrikes.
According to the latest UN figures, the Saudi military campaign has so far claimed the lives of over 1,400 people and injured close to 6,000 others, roughly half of them civilians.
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