Egypt charged 26 men, including three Britons, with trying to overthrow the Egyptian government to establish a new Islamic order.
The accused - including Britons Reza Pankhurst, Ian Malcolm Nisbett and Maajid Nawaz - also face other charges which include spreading propaganda for a group "established in breach of the laws and constitution".
Sixty other suspects, including a fourth Briton, Hassan Rizfi, have been released, the sources said.
A British embassy spokesman previously said the four Britons were arrested in Egypt in April. Embassy officials were not immediately available for comment.
The accused, suspected members of the Islamic Tahrir party, would stand trial in a state security court according to Egypt's emergency laws, the sources said.
Verdicts issued under emergency laws, in place since Muslim militants assassinated former President Anwar Sadat in 1981, cannot be appealed but Egyptian President Hosni Mubarak has the power to overturn them and order a retrial.
Islamic groups fought an insurgency against Mubarak's regime from 1992 to 1997 in which about 1,200 people were killed. The Egyptian government has arrested and referred hundreds of alleged Muslim militants to military courts since September.
Human rights groups say the government has exploited the U.S.-led war on terror to crack down on political opponents.