A fire started by Houthi rebel shelling started a fire that destroyed UN wheat stocks intended for distribution in Yemen as humanitarian aid. The UN's World Food Programme said it had 51,000 tonnes of wheat stored in silos at the Red Sea Mills on the outskirts of Hodeidah. Yemeni military sources said the rebels launched a mortar attack on the site near the port city on Friday, causing a huge fire in a grain silo and destroying a large quantity of wheat. The UN says at least 14 million Yemeni depend on aid to survive amid a humanitarian crisis caused by four years of war between the Iran-backed rebels and the internationally recognised government, which is supported by a Saudi-led Arab military coalition. "The attack is aimed at preventing a visit by a UN delegation to the mills today and to abort a potential agreement for facilitating food distribution to Sana'a and the towns on the shoreline," the sources said, in quotes reported by state news agency Wam. A team of UN monitors is currently in Hodeidah to oversee a ceasefire for the port city that was agreed at UN-brokered talks in Sweden last month. The sources said Houthi representatives on a joint committee to co-ordinate implementation of the truce were refusing to honour the agreement to open safe passages and allow mine-clearing operations along routes for distribution of relief. The UN World Food Programme has called for safe access to the grain silos to assess the damage from the fire, according a statement from the UN Office for the Coordination of Humanitarian Affairs (OCHA) on Saturday. "We are very concerned that some of our wheat stocks at the Red Sea Mills have been damaged," said WFP's Yemen director Stephen Anderson. The WFP has been unable to access the site since September last year, due to fighting, the statement said. "WFP urgently needs to get access to the Red Sea Mills so we can assess the level of damage and begin transporting the unaffected wheat stocks to areas of Yemen where it is desperately needed," Ms Anderson said. The UN agency's stores at the facility represent a quarter of its wheat stock in the country – enough to feed 3.7 million people for a month, the OCHA statement said. "The situation in Yemen is heart-breaking," said UN Humanitarian Coordinator for Yemen Lise Grande, in the statement. "A quarter of a million people are in a catastrophic condition, facing near starvation if assistance doesn't get to them. We need this wheat." In another shelling attack on Saturday, the rebels killed seven people and injured 30 others at a camp for the displace in Hajjah province, north of Hodeidah, <em>Al Arabiya</em> reported. In the central province of Bayda, five soldiers and a child were killed by rebel landmines, Yemen's state-run Saba news agency said on Friday . It quoted a military source who said the soldiers were trying to assist "wounded civilians targeted by another landmine in the same area".