Forty-six of the indicted members were arrested in various parts of Egypt on Sunday and are now in detention for 15 days investigation. The remaining six members are still at large, a security official said on Tuesday.
The security official, who spoke on the customary condition of anonymity, said the indictment states that as part of a plan to establish an Islamic state in Egypt, "they sent some Brothers to Palestine, Iraq and Chechnya to train for military operations".
A lawyer for the detainees, Abd Al-Munaim Abd Al-Maksud, rejected as false both the charge of sending men abroad for military training and the trying to overthrow the government to establish an Islamic state.
"The danger is that such accusations might lead to a military trial," he told The Associated Press. Since Egypt suffered an Islamic insurrection in the mid-1990s, the government has put scores of Muslim Brotherhood members on trial in military courts.
Curbing the Brotherhood
Rights groups have criticised the prosecution of civilians in military courts, saying they do not meet international standards of due process and their verdicts cannot be appealed to a higher court.
The detention of the 46 members appears to be part of an attempt to curb the Brotherhood. Its members say the government resents their role in protests against the US-led occupation of Iraq and pro-Palestinian demonstrations.
"The danger is that such accusations might lead to a military trial"
Abd Al-Munaim Abd Al-Maksud,
The detainees' lawyer
The Brotherhood is Egypt's oldest and largest Islamist group. Although it has been outlawed since 1954, the government allows it to function and it is known to have tens of thousands of supporters. It cannot field candidates in elections, but it endorses nominally independent candidates - who form the largest opposition bloc in the current parliament.
The movement formally renounced violence in the 1970s and says it strives for an Islamic state by peaceful means.