The U.N.'s office in Yemen said Sunday that Houthi rebels were still holding 20 of its staff following their raid on the organization's building in Sanaa, Yemen's capital, a day earlier.

On Saturday, the U.N. office said Houthi security forces had made an "unauthorized entry" into its compound.

"Five national staff and 15 international staff remain detained within the compound," Jean Alam, spokesman for the U.N. coordinator in the country, said on Sunday.