The head of the World Food Program says millions in Yemen face the risk of more deaths as aid deliveries cannot get to the needy because the blockade by the Saudi-led coalition is still in place.

Stephen Anderson says it's "heartbreaking" that millions depend on sustained access to humanitarian aid. Of a population of 26 million, some 17 million Yemenis do not know where their next meal is coming from and 7 million are totally dependent on food assistance.

Anderson told The Associated Press from Sanaa that humanitarian flights to northern, rebel-held part of Yemen have been grounded amid the blockade imposed by the coalition, following a rebel missile attack in Riyadh. The kingdom last week said it will reverse its closure of all Yemen's ports, after wide international criticism.