Amnesty International has said Egyptian authorities are not providing sufficient medical care to detained hunger-striker Mohamed Sultan, calling for his immediate release.

The organisation claimed in a statement Friday that Sultan, who has been on hunger strike for over 230 days, is at "imminent risk" of organ failure.

“Denying medical care to someone who is critically ill is not just callous and cruel, but blatantly unlawful,” said Hassiba Hadj Sahraoui, Amnesty International’s deputy director for the Middle East and North Africa programme.  

Last week, Freedom for the Brave — a grassroots movement calling for the release of political detainees in Egypt — said a prison official had told Sultan’s mother and a US embassy representative that Sultan could not meet them due to his deteriorating condition.

Sultan is currently in a prison hospital.

“Mohamed Sultan should not have been in jail in the first place and what he is accused of should not be a criminal offence. Now, the authorities are toying with his life in this manner,” said Hassiba Hadj Sahraoui. "He should be released without delay."

Sultan is detained pending trial with 50 others — including Muslim Brotherhood Supreme Guide Mohamed Badie — in the so-called “Rabaa control room” case.

They are accused of setting up an operation room after the violent dispersal of the pro-Mohamed Morsi Rabaa Al-Adawiya protest camp in mid-August 2013, as part of plans to defy the state and spread chaos, as well as plot attacks on police stations, private property and churches.

Sultan, 26, was arrested following the Rabaa dispersal. His family claims he was not involved in politics and had returned to Egypt to care for his sick mother.

His father, Saleh Sultan, a leading Islamic preacher and a member of the National Alliance to Support Legitimacy, a group opposing president Mohamed Morsi’s ouster, was rounded up by authorities in a crackdown on Morsi sympathisers.

Sultan's family has already launched a campaign in Egypt as well as the US to call for his release.

At least 80 people in Egyptian jails are on hunger strike against their detention and the country's controversial protest law, which was issued last November and is widely deemed restrictive. Hundreds have been arrested under its provisions.

In addition, a temporary hunger strike in solidarity with political detainees has been launched in recent days by at least 200 others, including families of the detainees, activists and journalists.