The U.N. says it is monitoring the redeployment of rebel forces from three key ports in Yemen after the government dismissed the withdrawal as a "farce."

Lt. Gen. Michael Lollesgaard, the head of a U.N. mission monitoring the cease-fire in Hodeida, says Sunday that monitors will verify the rebels' withdrawal from the ports of Hodeida, Salif and Ras-Issa on Tuesday.

The Houthi rebels say they began withdrawing on Saturday, in line with a long-delayed agreement reached in in December. Both sides agreed to withdraw from Hodeida, which handles 70 percent of Yemen's food imports and humanitarian aid, but remain divided over who will administer the ports after they leave.

A Saudi-led coalition allied with the government has been at war with the Iran-aligned Houthis since 2015.