Egyptian police have arrested about 50 members of the banned Muslim Brotherhood opposition movement in dawn raids in five cities including Cairo.
The organisation said those detained included doctors, engineers, civil servants and businessmen, adding that bank accounts had been frozen.
The offices and companies of some members were also shut down by police.
The authorities regularly take action against the Muslim Brotherhood, seen as Egypt's main opposition movement.
It is tolerated by the authorities and has 16 members of parliament, who were elected as independents.
The Brotherhood was banned in 1954 for advocating violent means to turn Egypt into an Islamic state but today it supports peaceful methods of change.
From the newsroom of the BBC World Service