The arrests are the latest in a crackdown by Egypt's new military-backed leaders against Islamists.
Egypt's state-run MENA news agency says Safwat Hegazy, a fiery Salafi preacher and top ally of the Brotherhood, was captured early Wednesday at a checkpoint near the Siwa Oasis, near Libya. He is wanted over charges of instigating violence.
Also, a security official says Mourad Ali, a spokesman for the Brotherhood's political party, was detained at the Cairo airport, trying to catch a flight to Italy. The official spoke on condition of anonymity because he was not authorized to speak to the media.