Egyptian authorities have renewed the detention of 16 members of the Muslim Brotherhood, defying a court order to release the men.
Officials of the banned but tolerated Muslim Brotherhood say the detainees include a senior official of the group, Khayrat al-Shater.
The Brotherhood's leader Mahdi Akef said Tuesday the decision to send the men back to jail means the government's call for political reform is not sincere.
The men were arrested in the latest round-up of Muslim Brothers which began in December after members of the group demonstrated wearing militia style dress.
The government has also frozen the assets of the men while it investigates charges of money laundering. A Cairo court is to review that case in late February.
The Brotherhood is the largest opposition bloc in the country's parliament, with 88 seats.
Reports say the government believes the Brotherhood is seeking to revive its underground military wing.
The group ran its candidates in 2005 as independents because it is not allowed to run them as members of a political party.
Constitutional reforms proposed by President Hosni Mubarak would, if adopted, formally ban religious groups from forming political parties.
President Mubarak, in a recent interview, called the Brotherhood a threat to Egypt because of the group's religious agenda.
The Brotherhood is calling for an Islamic state under Sharia but it does not advocate violent change.
Some information for this report was provided by AFP, AP and Reuters.