An international rights group says the recent arrests of a rights lawyer and an activist have raised fears of a fresh crackdown by Egyptian authorities on dissent.

Amnesty International said late Friday that Egyptian prosecutors ordered this week Haitham Mohammdeen and Mustafa Maher to remain in custody for 15 days over charges of "aiding a terrorist group," a reference to the banned Muslim Brotherhood organization.

The group says police arrested Mohammdeen after he was summoned Monday to a police station in Giza province, just south of Cairo, for accusations of violating probation terms. Maher was arrested on Tuesday at his home in a Cairo suburb.

Egyptian authorities, in an unprecedented crackdown on dissent in recent years, have often charged political opponents, even secular ones, with supporting the banned Islamist group.