The ICRC said Riyadh had released 104 prisoners.
The announcement comes after a prisoner swap at the weekend in which 887 detainees from the warring sides in Yemen were exchanged.
“Mother, I’m at the airport. Boarding on the plane in half an hour. I’m coming to Sanaa,” one former detainee, who has now been released, said while at the airport.
Two planes carrying 48 prisoners flew to Sanaa, while a third with eight captives headed for Aden, the ICRC's Jessica Moussan told The National.
“The unilateral release is not part of the simultaneous operation release that ended yesterday after three days,” she said.
Fabrizio Carboni, the ICRC's regional director, said: “Any respite for an exhausted population, including through release operations like these, is something to be supported. But ultimately, only a political solution will end the suffering in Yemen.”
On the second day of the exchange on Saturday, 16 Saudi detainees returned home from Sanaa.
Saudi Arabia's ambassador to Yemen Mohammed Al Jaber visited the Houthi-run capital for talks with the Iran-backed rebels and Omani officials to discuss the end of the war in Yemen and for negotiations on achieving political peace.