The United Nations renewed its plea to access food aid stored in mills for more than five months, to distribute in Yemen, where millions are on the brink of famine in the war-torn country.

The plea by the U.N. special envoy to Yemen, Martin Griffiths, and the U.N.'s humanitarian aid coordinator, Mark Lowcock, comes after an earlier request by the U.N. on Thursday.

"The World Food Programme (WFP) grain stored in the mills - enough to feed 3.7 million people for a month - has been inaccessible for over five months and is at risk of rotting," according to a joint statement by Griffiths and Lowcock.

"The urgency of United Nations access to the Red Sea Mills in Hodeida is growing by the day," they said. "We emphasize that ensuring access to the mills is a shared responsibility among the parties to the conflict in Yemen."