Egyptian security forces detained on Thursday a senior member of the Muslim Brotherhood’s Guidance Bureau, the group’s main decision-making body.

Egyptian security forces detained on Thursday a senior member of the Muslim Brotherhood’s Guidance Bureau, the group’s main decision-making body.

In a statement, the Brotherhood said Friday that Mohammad Saad Elewa had been detained while on his way to seek medical treatment in Egypt’s Giza province.

"The Muslim Brotherhood holds the criminal military coup authorities fully responsible for his [Elewa’s] safety," the group said.

Egyptian authorities have yet to officially acknowledge Elewa’s detention.

In late 2013, Egyptian authorities designated the Muslim Brotherhood as a "terrorist" group.

The ousted President Mohammad Mursi and most of the Brotherhood's top leaders, meanwhile, remain on trial in Egypt for an array of criminal charges, which they say are politically motivated.

Earlier this week, Mursi and scores of other Brotherhood leaders were sentenced to death on jailbreak charges.