A former aide to ousted Egyptian president Mohamed Morsi of the Muslim Brotherhood Islamist movement was released on Sunday for health reasons after 18 months in detention without charge, relatives said.

Khaled Al-Qazzaz, Morsi's former foreign affairs secretary, was arrested in July 2013 along with the elected president and eight other senior aides. 

Egyptian officials were not immediately available for comment on Qazzaz, who is one of the only Brotherhood figures to be released from jail since security forces killed hundreds of supporters of the group and arrested hundreds more.

Relatives said he was being held under guard at a hospital for the last two months after his health began to deteriorate following more than 400 days in solitary confinement. A U.N. panel said last year he was held unlawfully and should be released.

A medical report from the hospital where he was treated indicated that he should be released to receive proper treatment for his health problems, which include chronic high blood pressure, according to Ahram's Arabic news website. 

Qazzaz's relatives declined to comment on whether there may have been political motives behind his release.

"I'm not a politician, I'm just a wife and a mother and I'm just happy my husband is released and I hope we can be reunited soon," Qazzaz's Canadian wife, Sarah Attia, told Reuters by telephone.