The United Nations has declared its highest-level humanitarian emergency in conflict-torn Yemen, where over 80 percent of the population need assistance. U.N. officials have said the country is one step away from famine.

U.N. deputy spokesman Farhan Haq said humanitarian chief Stephen O'Brien convened a meeting of U.N. agencies and all agreed to declare a "Level 3" humanitarian emergency in Yemen on Wednesday.

The United Nations is already trying to respond to top-level humanitarian emergencies in three other conflict-wracked countries: Iraq, Syria and South Sudan.

In Yemen, Haq says over 21.1 million people need aid, 13 million face "a food security crisis" and 9.4 million have little or no access to water. He says 11.7 million have been targeted for assistance under a U.N. humanitarian response plan.