Al Jazeera has written to world powers asking them to secure the release of one of its journalists jailed in Egypt, accusing the authorities in Cairo of endangering his life.
In a letter directed at several individuals and institutions, Al Jazeera's lawyer said the health of Abdullah Elshamy, one of four Al Jazeera reporters being held in Egypt, was "of the gravest possible concern and in need of immediate attention".
Elshamy, who has been on hunger strike since January 21 to protest against his detention, is being held in solitary confinement in dire conditions, the letter said.
"Mr Elshamy's situation is of grave concern; his health is deteriorating and the Egyptian authorities show no sign of providing appropriate medical care or of bringing an end to his entirely unwarranted and indefensible detention without charge," Cameron Doley, the lawyer acting for Al Jazeera, wrote.
"Time is of the essence."
Elshamy, who is Egyptian, was arrested in Cairo in August last year while reporting on police dispersing supporters of ousted president Mohamed Morsi.
Elshamy is suffering from acute anaemia, the onset of kidney dysfunction, low blood pressure and hypoglycaemia, and his weight has dropped from 108 to 68 kilogrammes.
Recipients of the letter included US Secretary of State John Kerry, the European Union's foreign policy chief Catherine Ashton, British Foreign Secretary William Hague, French Foreign Minister Laurent Fabius, and UN human rights chief Navi Pillay.
Three other Al Jazeera journalists are being tried in Egypt on charges of aiding members of a "terrorist organisation", in a case that human rights groups say shows the authorities are trampling on freedom of expression.
All three deny the charges and Al Jazeera has said the accusations were absurd.
Egyptian officials have said the case is not linked to freedom of expression and that the journalists raised suspicions by operating without proper accreditation.
The trio - Peter Greste, an Australian, Mohamed Fahmy, a Canadian-Egyptian national, and Baher Mohamed, an Egyptian - were detained in Cairo on December 29.
Earlier this year, an Egyptian prosecutor said the Al Jazeera journalists had published lies harming the national interest and had supplied money, equipment and information to 16 Egyptians.