SANAA -- The United Nations World Food Program (WFP) has started a partial suspension of food assistance operation in areas of Yemen under the control of the Iran-allied Shiite Houthi rebels.

"The decision was taken as the last resort after lengthy negotiations stalled on an agreement to introduce controls to prevent the diversion of food away from some of the most vulnerable people in Yemen," said the WFP in a statement on Thursday.

"WFP's priority remains to feed the hungriest children, women and men of Yemen. But as in any conflict zone, some individuals seek to profit by preying on the vulnerable and diverting food away from where it is most needed," it said.

Saudi Arabia has been leading a coalition to fight in Yemen for more than four years in support of the exiled Yemeni government against the Houthis.