Egypt's banned Muslim Brotherhood says police have arrested at least 18 of its members.
The group says the police made the arrests on Friday.
The arrests come after Cairo police beat and detained demonstrators outside Egypt's Supreme Court on Thursday. The demonstrators were marching in support of judges who face a disciplinary hearing for calling last year's parliamentary elections fraudulent.
In those elections, Muslim Brotherhood members, running as independents, won 88 seats in parliament, making it the nation's largest opposition group.
During the election campaign, Egyptian security forces physically attacked voters in areas where the Brotherhood is popular.
Earlier this year, security forces arrested more than 12 members of the Muslim Brotherhood.
U.S. officials have indicated that Washington is displeased by the lack of progress in Egypt toward more democracy.
Emergency laws passed 24 years ago allow the Egyptian government to arrest people and hold them for long periods without charging them with a crime.
The Brotherhood has been campaigning for an end to the laws, which were passed after the 1981 assassination of president Anwar Sadat.