Relatives of Ayman Nour, the detained Egyptian opposition leader, said yesterday he had suffered a mild stroke or heart attack under interrogation.

Gamila Ismail, Mr Nour's wife, said his left arm and side had gone numb and he had experienced violent chest pains and sweating while being questioned late on Monday.

Mr Nour's detention has raised international concern. The Egyptian Organisation for Human Rights described his condition yesterday as critical.

Mr Nour, charismatic leader of a new, liberal political party - Al Ghad, or the Tomorrow party - was jailed in Cairo on January 29 then remanded in custody for 45 days on charges he had forged signatures for Al Ghad to receive official authorisation last year. His party insists the forgery allegations are false.