Updated

Senior aides held with ousted president Mohamed Morsi since Egypt's army toppled him nearly three weeks ago have asked their families for prison clothes, signalling possible charges, relatives said Tuesday.

Khaled El-Qazzaz, the former president's secretary for foreign relations, and top adviser Essam El-Haddad made the request in telephone conversations last Friday, their relatives told AFP.

The military, which overthrew Morsi on July 3 after mass protests demanding his resignation, faces international calls for the ousted Islamist leader's release.

It has refused to disclose his fate, and that of nine aides held with him, or their locations.

In a news conference on Monday, Morsi's relatives said they have not been allowed any contact with the deposed president and that they intend to sue the military for "kidnapping" him.

But relatives of Haddad and Qazzaz said they believed they were all still detained together with Morsi at a military facility, based on their telephone conversations.

The last contact was made on Friday, when Qazzaz called his home in Cairo and Haddad called his wife, relatives said.

"He called up his home and said 'I want white clothes,'" said Mona El-Qazzaz, his sister.

Prisoners awaiting trials or verdicts in Egypt wear white clothes, which may be provided by family members. They are issued blue uniforms after sentencing.

Two of Haddad's sons told AFP he called their mother, also on Friday, asking for white clothes. Other aides made similar phone calls, relatives said.

"Dr Essam called my mother on Friday and said I'm in good health, and he asked for white clothes," said one of his sons, Abdullah, a university student in Britain.

Following the calls, the relatives said they dropped off white-coloured clothes at the Abdeen presidential palace in Cairo, as had been agreed.

Qazzaz, one of Morsi's closest aides, had been allowed up to eight brief telephone calls with his relatives.

In his latest conversation, "He said 'don't wait for me,'" Mona, who lived in Britain, said of family holiday plans.

Rights activists say the detention of Morsi and his aides without charge violates Egyptian and international law.

"We consider that the way they are being held might to amount to an enforced disappearance," Hassiba Hadj Sahraoui of Amnesty International told AFP. "By now at the very least they should have been brought before a judge."

Heba Morayef of Human Rights Watch said Morsi and his aides were detained in a legal black hole.

"The fact that they have been held this long has been a complete flouting of Egyptian and international law without a prosecutor detention order," she told AFP.

"There is no legal framework for a lawyer to intervene."

Military officials were not immediately available for comment.

Prosecutors had suggested they might file a number of charges against Morsi, including conspiracy with foreign actors and insulting the judiciary.