By Maggie Fick

CAIRO (Reuters) - The family of Egypt's ousted Islamist president, Mohamed Mursi, said on Monday it would take legal action against the army for abducting him.

Mursi has been held at an undisclosed military facility since the army deposed him on July 3 and suspended the constitution in the wake of huge street protests against his one-year rule.

The army says Mursi is being held for his own safety. His detention and the arrests of numerous senior members of his Muslim Brotherhood have fuelled fears of a broad crackdown against a group banned during Hosni Mubarak's 30 years of autocratic rule, until he was toppled by street protests in 2011.

"There is no legal or constitutional basis ... for detaining someone not accused of a crime for his own safety," Mursi's son, Osama, told a news conference.

He said the family would take immediate legal action "inside Egypt and at an international level" against Abdel Fattah al-Sisi, the army commander and defense minister who played a central role in forcing Mursi from office.

The Muslim Brotherhood accuses the army of orchestrating a coup that has triggered violent clashes and exposed deep fissures in the Arab world's most populous nation, a strategic hinge between the Middle East and North Africa.

The Brotherhood says it has had no contact with Mursi since he was overthrown, and that it believes he has not had access to a lawyer. Osama said the family had also not been able to contact him and had no information on the state of his health or where he was being held.


He described Mursi's removal as "nothing less than the abduction of the will of the people and the entire nation".

Mursi's supporters are maintaining a round-the-clock vigil in a Cairo suburb, now in its third week. They say they will stay put until Mursi is returned to office. A few thousand of his supporters protested outside the High Court in central Cairo on Monday.

The military has installed an interim cabinet and promised a new election under a constitution now being amended to replace one drafted last year by a body dominated by Islamists and approved despite objections from Christians and liberals.

Egypt's public prosecutor's office launched a criminal investigation against Mursi on July 13, saying it was examining complaints including spying and inciting violence. It did not specify who had filed the complaints. No formal charges have been announced.

Mursi's daughter, Shaimaa, told the news conference that the family held the army responsible for his safety.

Heba Morayef, Egypt director of Human Rights Watch, said that, without a detention order from the prosecutor's office, there were no grounds to hold Mursi without charge beyond a maximum 48 hours.

"(Mursi's)arrest and that of his advisers is completely illegal," Morayef said.

Gamal Abdel Salem, a doctor who spoke alongside the Mursi family, said Mursi suffered from diabetes, and that a doctors' union had asked for access to him.

(Reporting by Maggie Fick; Editing by Matt Robinson and Kevin Liffey)