The official Saudi Press Agency reported today that the two were arrested in Riyadh. It said the Filipina sewed explosive belts for the Syrian and that bombs were found at two sites.
Authorities say they safely evacuated the area around both sites and defused the bombs.
The agency identified the Filipina as "Lady Joy" and the Syrian man as Yasser Mohammed Shafiq al-Berazi. It wasn't clear if they had lawyers and Saudi officials could not be immediately reached.
The agency report offered no motive for the alleged plot. A local Islamic State affiliate has claimed a series of recent attacks.